Microsoft generally doesn't worry about losing market share to Linux over games. They don't even worry about losing desktop share for the public sector. Only businesses matter, and they have heavy vendor lock in there as Microsoft Office, Teams, and to a lesser extent, Azure, keep them subscribed/enslaved.

Microsoft also gives a shit ton of money to the Linux Foundation,along with the rest of MMAANG and many other companies. All these companies know Linux runs the back end servers, and its free for them to use however they want, and they have a vested interest in Linux being around for servers as even they are aware it's superior for that specific purpose.

Microsoft runs the Desktop, Apple runs the phone, Google and Amazon compete for cloud, and Meta owns marketing. Sure, they sometimes compete in other spaces like Android and Azure, but those are generally the established fiefdoms.

And Linux is all of their removed, but also all of their main support beam without which nothing works.

The true underdog is BSD.