The explanation I remember seeing many years ago, no idea how true it is, was that this was entirely about purchasing.

There were (are?) companies and especially parts of the government where it was pretty difficult/impossible to purchase anything that wasn’t on an official pre-approved list. Trying to get anything new added was a massive problem.

One of the things that was on the list was something like “a computer running Unix“. Tada. Macs now run Unix so you can easily buy them.

Like other people here, I really don’t think true compliance mattered to basically anyone for their actual use. The idea that it was just box checking so they were easier to buy in some institutional environments makes much more sense to me.