Why does it say nothing about the 1989 protests on Tiananmen Square, Beijing?

I think the bigger question is if this is mostly for a Chinese audience why do they need to mention the event everywhere? How long do they need to keep self flagellating until they have made penance and will be forgiven for whatever transgressions occurred?

And why would they need to promote it on a tourism website?
It is not only for a Chinese audience, no. It is about a government's lack being being able to admiss guilt, countered with censorship to forget that mistakes ever happened, instead of trying to learn from past mistakes.
"In opposing subjectivism, sectarianism and stereotyped Party writing we must have in mind two purposes: first, "learn from past mistakes to avoid future ones", and second, "cure the sickness to save the patient". The mistakes of the past must be exposed without sparing anyone's sensibilities; it is necessary to analyse and criticize what was bad in the past with a scientific attitude so that work in the future will be done more carefully and done better." - Mao Zedong, ["Rectify the Party's Style of Work" (February 1, 1942), Selected Works, Vol. III, p. 50.*]
- Baidu baike is not owned by the government though

Adding to RoomAndBored's comment

https://lemmygrad.ml/comment/460227

Even a quick search of this term in Baidu will bring up results with the term 政治风波.

This search results page is tampered. You use an uncommon search query (1989政治风波 = 1989 Political Turmoil, a strong euphemism, instead of "unrest" or "demonstration", " protest") to get specific results, probably for exactly this reason: plausible denialbility.
If you click on the first result, the only thing said about the protests is one small sentence at the very end (that again uses euphemisms and is even just downplaying the event by just not talking about it that long), like it just happened casually on the side. To quote directly in chinese, since I am appareantly a 'stupid westerner, not understanding the chinese language and posts articles about numbers':
"与此同时，据说有上千万农民在城市中寻找工作，结果就迅速发生了一系列抗议、罢工和游行示威行动，最终导致了1989年的政治风波。" - https://news.ifeng.com/c/7fc9V5NzCYr
Yeah, just farmers looking for work, making a little unrest.
The rural population did not even participate in the protests, except if a student was from a rural area maybe.
Or another quote from another result:
"1989年春夏之交在首都和一些地方发生政治风波，党中央采取了断然措施予以解决。" - http://www.93.gov.cn/lshm-dsj/253321.html
Yeah, some small turmoil occurred, but has dealt with. Same stylistic elements as the first example.
I could go an all day, all of the petty attempts of trying to get me into an absurd argument with petty provocation, I am not that stupid.
- From an article linked:
  长期以来，一些西方国家的政治势力有计划地通过种种渠道对社会主义国家进行思想、政治渗透，竭力支持和扶植各种反共反社会主义活动。八十年代末，东欧一些社会主义国家开始出现动荡。西方敌对势力加紧推行和平演变战略，通过多种渠道对中国施加影响，使国内搞资产阶级自由化的人受到鼓舞。由于在一段时间里，党内少数领导同志在推进改革开放，大力发展经济的同时，对坚持四项基本原则缺乏一贯性，忽视党的自身建设和社会主义精神文明建设，思想政治工作受到削弱，少数干部中滋生了相当严重的腐败现象，损害了党在群众中的威信和社会主义在人们心目中的形象。致使一度收敛的资产阶级自由化思潮再度泛滥。1989年春夏，极少数反共反社会主义分子利用党在工作中的失误和人民群众对物价上涨，特别是对一些干部中腐败现象的不满情绪，进行煽动反对共产党的领导、反对社会主义制度的活动。他们借群众悼念胡耀邦逝世这件事，大肆散布谣言，掀起一场有计划、有组织、有预谋的政治动乱，并在北京地区煽动一些不明真相的人占据天安门广场，冲击党政首脑要害部门，制造反革命暴乱。在关系党和国家生死存亡的关键时刻，党中央总书记赵紫阳犯了支持动乱和分裂党的严重错误。中央政治局在邓小平和其他老一辈革命家坚决有力的支持下，依靠人民，旗帜鲜明地反对动乱，并采取果断措施，在6月4日一举平息反革命暴乱，捍卫了社会主义国家政权，维护了人民的根本利益。
  6月9日，邓小平接见首都戒严部队军以上干部，并发表讲话指出：这场风波迟早要来。这是国际大气候和中国自己的小气候决定了的。他要求全党，很冷静地考虑一下过去，也考虑一下未来，对的要继续坚持，错误的要纠正，不足的要加点劲。他以斩钉截铁的语言阐明了当时必须作出明确回答的重大问题：
  党的十一届三中全会制定的路线、方针、政策，包括我们发展战略的“三部曲”没有错；党的十三大概括的“一个中心、两个基本点”的路线没有错。如果说有错误的话，就是坚持四项基本原则还不够一贯，没有把它作为基本思想来教育人民、教育学生、教育全体干部和共产党员。我们原来制定的基本路线、方针、政策，照样干下去，坚定不移地干下去。
  1989年6月23日至24日，党召开十三届四中全会。鉴于赵紫阳在制止动乱的关键时刻所犯的严重错误，以及他主持中央工作以来，由于消极对待坚持四项基本原则给党的事业造成的严重损失，全会决定撤销他所担任的党内一切领导职务，并对中央领导机构部分成员进行调整。全会选举江泽民为中央委员会总书记；增选江泽民、宋平、李瑞环为中央政治局常委，政治局常委会由江泽民、李鹏、乔石、姚依林、宋平、李瑞环组成。江泽民在会上表示：这次中央领导核心虽然作了一些人事调整，但是，党的十一届三中全会以来的路线和基本政策没有变，必须继续贯彻执行。在这个最基本的问题上，我要十分明确地讲两句话：一句是坚定不移，毫不动摇；一句是全面执行，一以贯之。通过这次全会，党中央明确宣告，党的基本路线和十三大的决策，绝不会因为发生这场政治风波而动摇，从而使党在惊涛骇浪中坚持了建设有中国特色社会主义的正确航向。
  在十三届四中全会召开之前和全会以后，邓小平多次郑重提出：现在要真正建立一个新的第三代领导。第三代的领导集体必须有一个核心，要有意识地维护这个核心，就是江泽民同志。他强调：中国的问题关键在于共产党要有一个好的政治局，特别是好的政治局常委会。只要这个环节不发生问题，中国就稳如泰山。他一再表示：新的领导班子一经建立有秩序的工作，我就不再过问。一个国家的命运建立在一两个人的声望上面，是很不健康的，是很危险的。新的领导要一切负起责任，放手工作。“这就是我的政治交代”。
  1989年9月4日，邓小平向中央政治局正式提出辞去中共中央军事委员会主席职务的请求。两个月后，党的十三届五中全会批准邓小平的这一请求，同时决定，江泽民为中共中央军事委员会主席。全会认为，邓小平从党和国家的根本利益出发，在自己身体还健康的时候辞去现任职务，实现他多年来一再提出的从领导岗位上完全退下来的夙愿，表现了一个无产阶级革命家的广阔胸怀。全会对他身体力行地为废除干部领导职务终身制作出表率，表示崇高的敬意。
  从十三届四中全会到五中全会，以邓小平为核心的第二代中央领导集体和以江泽民为核心的第三代中央领导集体实现了顺利交替，保证了党的政策的稳定性、连续性和国家的稳定，使社会主义改革开放和现代化建设能够继续前进。这是党在政治上高度成熟、组织上坚强有力的明证。
  RoomAndBored has linked to the official statement which is probably as detailed as it will get.

Here is ProleWiki’s article.

It might not be mentioned because, although there were protests in the square, all deaths were in streets near the square instead of in the square itself.

There is also nothing metioned on June 4 concerning any protests: https://wapbaike.baidu.com/item/6%E6%9C%884%E6%97%A5
- Dude, that’s just an article on the literal number 6. Lmao
Most of the sources there cant be verified, don't exist or contradict the article
- Examples:
  Don't exist: [2] https://www.mango-press.com/the-tiananmen-square-massacre-the-wests-most-persuasive-most-pervasive-lie/
  Can't be verified: [1] Vancouver Sun, article written in a google doc, authenthiticity can't be proven, source of source in bottom is a link that doest not work.
  Contradicts the Prolewiki article: [13] CBS News,
  Quote: "But there's no question many people were killed by the army that night around Tiananmen Square, and on the way to it — mostly in the western part of Beijing. Maybe, for some, comfort can be taken in the fact that the government denies that, too."
  Hyperlink in quote leads to dead page, so archived link: https://web.archive.org/web/20090606124946/https://www.cbsnews.com/blogs/2009/06/04/world/worldwatch/entry5061564.shtm l: "We could hear shooting. A large group of students and civilians at this corner of Tiananmen Square were facing lines of soldiers.
  We could see burning vehicles on the Square and we tried to approach discreetly, but were told the soldiers would certainly shoot."
  Quote from ProleWiki article: "Around 5:00 am on June 4, the 3,000 remaining protestors peacefully left the square. No one died in the square during or after the protests and most deaths were caused by the foreign-backed faction of students."
  You see? The sources are very bad, their contents also twisted around, like in [13]; the source was used to "proof" that "[n]o one died in the square [...]" and "[...] deaths were caused by the foreign-backed faction [...]". If you would use this kind of sourcing in any scientific work, everyone would laugh at you.
  Don't let yourself be blinded by the 'truth' that sounds the most comforting

It's probably censored because it's a politically sensitive topic. From my reading, the article is meant to promote tourism and pride in national monuments, not to discuss history in detail. Mentioning those events is seen as encouraging social unrest.

Why do they need to censor it?
- All current actually existing socialism is in a defensive stance. This is needed because of the history of bourgeois liberal democracies seeking to destabilize and collapse socialist states by any means necessary. Socialist states that didn't do a good enough job of defending themselves are no longer with us largely because of such actions. This is precisely why government censorship exists in China, to help maintain the social order and ensure stability of the socialist state. Stability is especially valued in China for historical reasons. Other AES countries like Vietnam also censor things like hate speech or misinformation to some extent, including jail time for the worst offenders.
  For Tiananmen Square specifically, there's a huge misinformation campaign from Western countries about the events of the protest. If you go up to a random Westerner, show them the iconic photo of the man in front of the tank, and ask them what happened to the man, they will likely tell you that the man was run over. This is, of course, not what happened, and there's video evidence to this effect. But the misinformation in the West is hegemonic and entrenched, and if it got around in the PRC, it would take a lot of time and effort to debunk it and not everyone would believe you anyway. So, for the Chinese government, they prevent people from bringing it up more than absolutely necessary by censorship. It's not the ideal solution but it will have to do for now.
  If that is enough to squick you out about MLism you should do some introspection about why that is. If you're truly committed to revolutionary politics you may find yourself needing to do much worse than censorship in the future. It is necessary for revolutionary movements to strike a balance between achieving their goals and avoiding the worst excesses of revolutions. As we know from history, this can be quite a difficult balance to strike, especially if the people have had a boot on their neck for a long time and are full of righteous anger. We need people like you in our movements to rein us in, but not so much that the revolution fails and all of it was for nothing.
- Info on TinSquare isn't censored, you can find it in the Chinese web, they don't hide anything about it (because there is nothing much to hide!). But as bobs_guns says, if the info is already available, does it need to be on every mention of TS, especially for a touristy site?
Since when do encyclopedias promote tourism? Those are photographs taken by tourists. Also, why are politically sensitive topics censored? I do not understand this, they are not censored in other communist parties, groups.
- Also, what does politically sensitive mean?

How about this, why doesn't it mention the October 28th 2013 terrorist attack? https://baike.baidu.com/item/10%C2%B728%E6%9A%B4%E5%8A%9B%E6%81%90%E6%80%96%E8%A2%AD%E5%87%BB%E6%A1%88/12022667

On 1989 Political Disturbance: https://lemmygrad.ml/post/1252700

Also not mentioned on gov.cn website (no June 4):

https://www.gov.cn/xinwen/2021-06/28/content_5621160.htm

That page is about the CPC milestones and achievements. The 1989 event obviously wouldn’t be on it.
- It is though, just not July 4th.

This makes me lose faith in Marxism-Leninism by quite a bit, governments that cover up their "mistakes" and can't admit them, do not govern in the interest of the people, only in the state's.

They’re not “covering up mistakes;” they’re stopping Western disinformation on the event (such as that it was a “massacre” of “peaceful” “anti-government” protestors)
Other comrades can provide you links to our many threads on this subject.
- I am practicing democratic centralism here lol. But appareantly, criticism, that is based on facts, is not wanted here. Just "unity in debate, unity in action" hahah