Even if it was all gamers, that'd push a lot of companies to care about Linux a whole lot more. Venn diagram of people who spend a lot of money in tech stuff and people who play games is almost a circle nowadays.
I've worked in server-side systems development for over a decade, in all sizes of company, and Linux has been ubiquitous on the server side for ages: it's simply the most problem free way of maximizing the hardware you have, not to mention cheaper (both upfront and TCO).
I don't even think Valve really care about Linux. At least not in the same way that Linux users care about Linux.
They just care about getting the costs of Steam Deck down, and don't want MS to go mental and pull the rug from under their business model.
I'm surprised by how much of my Steam library would work on the Deck, tbh. Out of nearly 1300 games, 407 are verified, and 931 are verified and playable. Be nice if you could stream the rest (either from your own PC or an external provider), but Geforce Now showed that was a minefield (I suspect due to exclusive streaming rights already being to sold to someone else) and publishers freaked the fuck out, despite it being none of their business where I run my purchased games.
They care about Microsoft not 100% controlling access to the platform Steam customers use. Valve cares about Linux because they need an escape strategy if Microsoft ever locks them out.
I thought they were going that way with Windows 11 S that prevented you using anything other than the MS Store, but it turns out you can just switch S mode off.
It would be mental for MS to do it. Their desktop dominance hinges entirely on people still being able to run the last 30 years or so of wonky old software.
S mode is in 10 also. I work for a MSP that recommends virtual desktops to our clients, so we often have to help users connect from their home PCs. It wasn't a ton, but enough people were locked in S-mode we all had practice walking them through disabling It, because it blocks our remote control app also if in s made.