When I did a 4 year CS degree at a UK university in the 1980s I don't think I touched anything from Microsoft for the entire time I was there!
For other degrees you need software which only runs on Windows.
It might also help that Microsoft was totally irrelevant in the professional world in the 80s.
Like yeah if you have a lot of pre-existing infrastructure migration can be a pain but MS is not in anyway necessary.
There is a lot more happening in the administrative and infrastructural side of things in most universities that one barely observes as student. So every change needs to take also that into account, the management and maintenance of services and infrastructures that must reliably support thousands of users, with relatively strict privacy and security standards, and their migration.
It just didn't seem right. Why would you need that?
What if you just wanted a plain IBM computer? Why isn't that the mainstream without need for any third party software? Or is it software? How do people do without it? What if you just want to compute? Not use the PC as an office machine or do any gaming?
Is this Microsoft content really essential?
Isn't the hardware any good without a Microsoft?
How would you go about doing that?
I guess Linus eventually asked himself the same kind of things and drove it home :)
unfortunately the university has gone full MS since then