Forking Linux and continuing to do that instead of up streaming is a massive task, especially as time goes by and code similarities drift. It’s much better to upstream. This is why fortune 500 companies contribute to the Linux kernel.
The old guard in the Linux kernel have a real stick up their ass against anything not C, despite Linus himself advocating that rust drivers should at least be looked at. It’s turned off a lot of new blood doing projects like Asahi because they don’t have upstream support so the burden of the project is much too great for a hobbyist endeavor for something that should otherwise be fun and mentally engaging.
Microsoft doesn’t actually care because most of their revenue is from corporate environments tied to the OS and their cloud offerings. Everyday users are nothing to them, which is why they don’t try harder to keep you from using unactivated copies of windows. You are nothing