They tried to rewrite the OS in a C# derivative and could never meet the perf needed while still fighting backwards compatibility issues[0]. At this point mobile OS's are a lost cause, but the PC market is stable. Windows server has never been as big as Linux, but all of Azure runs the Windows hypervisor. I'm not sure they're losing at all actually. [0]: https://en.wikipedia.org/wiki/Midori_(operating_system)