IS the multiplatform aspect one of the reason why the
kernel as such
worked so well ?
It was designed by a crew of ex DEC people who knew WTF they were doing
after having built a couple of kernels from the ground up.
They did quite well for themselves as a result of being in the right
place at the right time.
The rest of the system is the result of the project management cluster
fsck that is MSFT.