As a person who cares about the gaming ecosystem, I think it would be really healthy for Microsoft to not have full market dominance.

They're busy making studio acquisitions which are gradually centralizing the market, which could become very problematic if they start taking anticompetitive approaches to distribution.

More people on Linux means more pressure for software availability on Linux, and if people can just move over relatively easily that prevents Microsoft from going full corpo-digital-prison-hellscape.