Literally the biggest reason why Windows is still a thing in desktop is DirectX exclusivity, which makes games (the good ones anyway) exclusive to Windows.

If gamers had a choice, they wouldn’t be on Windows anymore, which would then forcefully drive everything else away from it on the desktop. Drivers thus performance and compatibility would be moved and with it the viability of a fully customizable system (gamers love that) would quickly erode Windows.

The other thing Windows has to keep it alive is Office but that alone won’t keep it mainstream. That would only keep it alive until a worthy competitor came along, which would probably not take long as soon as all gamers moved to Linux as then that would become a big market gap (temporarily filled with web based office tools)