It comes down to how much the publishers care about their own product. Devs shoveling third party kernel anti-cheat into their product often cause those games to be Linux incompatible. Devs bundling their own unnecessary launcher with the game and requiring it to run the launcher in order to run the game sometimes cause those games to be Linux incompatible. It often isn't even the devs themselves making this decision, which is why I blame the publisher more than the developers in most cases.

But with how robust Proton has become these days there isn't a whole lot outside of those two cases that will make a game not run on Linux. It's pretty intentional at this point.