We don't need research because QNX, L4 and many others on embedded space do exist as well.
Apple was not a bastion of quality in the 90's. They couldn't modernize the Mac OS, and that continued with little more than window dressing over what was released in the 80's. The Mac line up was a horrible mess of barely different models that needed a Ph.D to figure out what was different. The company was bleeding money and seriously close to bankruptcy.
The Apple of the mid 90's wishes it could release something like Tahoe.