@mint My ex-boss Who-iggins used to tell me that DOS was what was lifted from VMS. I know there was fear from the Microsoft side that NeXT was on the right track and could eat their lunch==>NT
The NeXT crew was very small so they were able to do initial implementation but had a tough time keeping everything up to date. That was fixed when they "acquired" Apple hehe and got flooded with cash
Mach progress had slowed coz they were poached... but almost a decade had passed so there was progress