With Microsoft specifically there's also the fact that it made a massive investment into rebuilding a large chunk of its campus in the last few years (IIRC it began before COVID). They demolished some of the oldest buildings - the ones that were done back when every senior engineer was entitled to an office of their own - and replaced them with "open office" cubicle farms.

Now, I would imagine that there are quite a few in the top management who originally signed off on that expense. Probably the same people who were talking about replacing offices with cubicles since 2015, which means Satya and his inner circle. So now they've spent a lot of money, they have to do something to show to the board that it wasn't wasted. Which means filling those buildings with employees, whether they like it or not.