Even with your clarification, I think I touched on that. Steam isn’t trying to push companies to develop for Linux, instead they are trying to make Linux more compatible with games. That’s why they’ve talked wine and turned it into a very game specific thing called proton.

If they wanted to push people to develop for Linux, they wouldn’t put so much time and effort into developing something that removes that need

Simply put, they don’t need to. Linux might be a tiny percentage of the market but thanks largely to steam deck it is growing, which means it’s starting to become more worth it for companies to make sure their game works on it.

Secondly, thanks to proton, some games don’t even need to be modified to support Linux or the steam deck. I play plenty of games that are listed as unplayable or unverified on my steam deck, and sometimes it is listed that way because of one or two minor things that haven’t broken the game for me.

And lastly, as every major company has found out one by one, it’s worth it for them to pay the 30% to get access to steam users.