>>11853897 (OP)Most of the reasons people have given are wrong or ignore history.
We call it "PC Gaming" not Windows gaming, because it's been a thing since DOS/the original IBM 286 PC. In the 80s, there were many competing computing platforms with their own software/gaming ecosystems, DOS was one of if not the largest. The only thing really close to being as successful was Commodore with the Commodore 64 and Amiga, but DOS edged them out because it was popular for gaming and office software and the Commodore machines were really only popular for gaming/photo-editing/multi-media work. DOS persisted as a mainstream gaming platform all the way into 1996, when it was getting full 3D software rendered games like Quake and Daggerfall.
So Microsoft always had a head start in Computer Games, because "PC Gaming" doesn't really mean computer games, it means, "Games on a Microsoft Platform," because before the 90s we also had "Amiga gaming" etc. After Microsoft killed all their competitors on desktop circa 1995, Linux began to catch on in the tech industry entirely because you could set up what's called a LAMP stack (full server environment) without paying any license fees, or at worst paying them to Red Hat, who was cheaper than Unix/Microsoft. While this was going on, Microsoft correctly identified 3D as the next big thing in gaming and developed and heavily marketed DirectX as an alternative to OpenGL. In a few years, most games would ditch Software Rendering and require a dedicated Graphics Card and DirectX. So before DirectX/Direct3D games were tied to Microsoft via DOS, and after DirectX games were tied to Microsoft because they often only had a DirectX renderer. And all this DirectX stuff ran extremely low-level on your graphics hardware, meaning Microsoft needed a very close and direct relationship with companies like Nvidia and ATI. They used this relationship FOR DECADES to ensure the drivers on linux sucked shit until like 2016.
tl;dr Windows IS PC Gaming, sadly.