And it helps enhance their other products. Your home computer has always come with windows. So your employer buys it for everyone because everyone understands it. Maybe they have you use Mac if you’re an artist or dev. But since you’re on windows you’ll use office, and it might cost you a bit, but they’re more concerned with your employer buying it for you. Hell you probably have office at work even if you’re on mac. And from there each and every new thing they add is part of their ecosystem with all the trust of “it’s from Microsoft, it’ll work”
It’s easier and more corporate trustworthy to just buy Microsoft and the only thing that can challenge that is if enough people not only don’t use it at home, but actively are worse with it than something else.