Of course this isn't just relegated to Marxism though the article focuses on it. There is broadly across the west this myth of peaceful resistance, of the noble peaceful resistor, of the noble martyr whose death brought about change without ever lowering or debasing themselves to shedding blood or engaging in violence themselves. This broadly connects back to the Christ mythos, Christ a figure who was martyred so the Christian religion says to save all of humanity. He died nobly we are told because he did not call upon all the powers of heaven to smite the oppressors, because even in his dying throes of agony he screamed "father forgive them" to stall the wrath of heaven. And through his glorious, noble, peaceful, pacifist sacrifice we are told all may have eternal life through belief rather than perishing.
So the west is very obsessed with this idea and it stems from I believe this and of course is actually propagated in school teaching and so on with figures like MLK and Ghandi because it supports the hegemonic domination of the west, the submission of the proletariat, perpetuates ineffectual tactics which are handily beaten down with laughs and hands the participants trophies while regaling them with revisionist tales of how it didn't work this time but it did this other time as long as you ignore all the violence and other pressures that actually led to the victory falsely claimed in the name of non-violent, peaceful, and non-disruptive protest.
Good read. But I don't necessarily agree with the correlation of admiring defeat as a direct connection to Christianity, but rather the way the west is conditioned to find a way to win. If some Socialist movement failed, it is glorified in its failure because the hyper competitive West must extract some kind of victory. To utterly lose is to potentially admit eternal defeat and abandon a path as impossible, so already downtrodden Western leftists are keen to extract a moral victory or sense of heroic martyrdom.
Also much of what would account for leftist celebration of these failures, is actually Liberals co-opting historic evidence. For example I interpret the celebration of non-violent means that have yet to produce any revolution as simply Liberalism. If one would cheer on the status quo while dreaming of a slightly more perfect utopia, then they are going to romanticize the people that fought for a better future, only to be "cut down by reality". Liberals celebrate these people for their ideas but not their actions, unless of course their actions accounted for nothing. If they ennoble a failed leader or idea, it is because they want to celebrate the status quo crushing those who would challenge it, but admire their "heart being in the right place". Or Liberals interpret the fallen hero or movement's actions as a means for reinforcing the challenged status quo, as opposed to changing it.
It does explain some level of psychological copium that is used by Western leftists to glorify defeat, but I don't think it is the driving force behind the defeat itself. I would presume the reason Socialism doesn't get off the ground in the West is the lack of material challenge that it's populations experience by benefiting from their imperialism. No collectives form from a need for survival unlike the East and Global South that are subjected to imperialism and poverty. For these regions, Socalism is a source of strength. While for the West, Socialism is an aesthetic or higher moral purity, which is the reason it never goes anywhere. It isn't seen through the lens of survival, but often just contrarian rejection or individualistic rebellion of a system that isn't serving that persons best interests.
Though I absolutely agree with your sentiment that these ineffective tactics are hammered into children at a young age to be admired for their virtue and lack of results. But I would regard that as institutions of capital protecting themselves from any future overthrow, not because "it was what Jesus would do".