Including a Linux kernel is really the nuclear option: rather than trying to fit Linux applications in Windows, they're running in their own world and providing integrations into this world.
The was that the NT kernel was still sufficiently different that the filesystem performance was quite poor and complex applications like Docker required more kernel features than was provided by just the syscall API. WSL1 did what the guys from Illumos and FreeBSD have also done: since the Linux syscall interface is quite stable, the NT kernel can simply implement these syscalls and handle them appropriately. No, Microsoft is not about to remove the NT kernel. The inclusion of a Linux kernel really seems to cause a lot of confusion. I find it fairly easy to work on both Mac OS X, Linux and WSL2 - but not pre-WSL Windows. If the stack we care about is open-source and runs across many systems, then we still have the freedom. This system wasn't as open-source as Linux, but it was good enough: Most of us don't want to mess about with the desktop stack. This really helped the Mac take off among hackers.
In the mid 2000's the Mac really took off due to being a good-enough Linux replacement on the command line, while taking care of all the hardware integration and providing a sleek desktop experience.
This is really Microsoft catching up to the Mac in terms of integration with the open-source ecosystem which importantly drives the web.
