I don’t know about that “adults” comment. Microsoft grew their operating system up from a very low base where the “adults” moved theirs down. For most users, windows NT was ridiculous overkill.
At the time most users and businesses didn’t own a PC that could do the virtualisation tricks required by windows 3 (o windows 2 386). A lot of places still had XT class machines right up to the end of the 1980s.
So the Microsoft guys had a pretty complex landscape in which Windows had to operate and they managed a fantastically complicated solution. They were definitely adulting hard during that time.
I didn't mean to imply there was something "less" about the talent creating the DOS-based Windows OS. I think it's a marvel of engineering for economy and constraints.
I think NT was a means to an end (government contracts requiring a "Rainbow book"-qualified OS). It was a long time before the DOS-based Windows OS lost its position as the consumer / business offering. I think that shows MSFT knew what they had in that legacy code and leveraged it for great profit for a long time.
I think the "adults" came in and made a stuffy buttoned-down operating system meant to qualify as a "C2"-compliant OS meant to win contracts. NT doesn't have the hacky charm of the DOS-based Windows versions.