Problem is that the Linux kernel is in somewhat good shape because Linus is a controlling asshole, especially looking at the shit he rejects.

One of the most important rule is that to NEVER BREAK USERSPACE COMPATIBILITY. Imagine Mozilla kicking out all the extensions because they made an update to the Firefox backend, nobody will tolerate that level of bullshit every few weeks especially if you live on the bleeding edge kernel. It takes a firm hand to say no when faced with the powers that may be.

Big tech mega corporations ironically are the biggest code contributors to the kernel. Intel already wanted Linus removed for questioning their kernel commits especially around the hardware RNG driver and Spectre/Meltdown fixes, which coincidentally was when the big fuss about Linus being rude and unprofessional hit mainstream consciousness. Since all the technical information on the hardware implementation side is under NDA, nobody can know why the code is even done that way.