Valve is definitely an exception. I am not sure why, but it is pretty much in the open that Gabe Newell has a bone to pick with Microsoft and he has been throwing money at Linux for over a decade to break their monopoly on gaming. I'd argue that this has nothing to do with their love for the community and more so with Gabe's personal vendetta against Microsoft.

Reality is that most game devs, most executives and most people in marketing don't really care about Linux. It is good PR to support Mac and Linux, and some of the geekier developers will go the extra mile to support it, but I think it is common in the industry to assume that Linux users are not gamer, or that they have enough knowledge to install a dual boot. They don't care in the sense that they don't even think about it, its not even on the radar for most game companies. Most studios probably never even had a discussion about it. That is how irrelevant Linux has been to gaming. Hence why Proton is such a tour de force.