There is a deep logical flaw. One does not has a significant smaller pond by being exclusive for Linux. Because you do not compete against other Linux exclusive games. You compete against every game that is exported or crosscompiled to Linux, plus every game that can run under proton or wine with ease and every game that is platform indipendent, like html games. Or even good bad Java.
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Proton and Wine is only the icing on the cake. The real problem is, that many popular games that are small time indie have exports for Windows, Android, Mac and Linux. The reason being, as I suspect, is the use of engines.
And just like games get often asked about android or mac releases, if you post a popular linux game, you would get pestered for a windows release. If the libraries used are available as open source (and we are talking about Linux here ;-) chances are, that a windows build is trivial in theory.