[btilly]

According to the public advertising at the time, Windows NT, GNU Hurd, and Mach were all designed as microkernels. Mach of course is the basis for OS X.

At the same time that Windows NT was being claimed as a microkernel, Linux was outperforming and had a reputation as being more reliable. Ditto with Mach. And GNU Hurd famously was hard to get running at all.

QNX is highly reliable, but is also a specialized use case.