Everyone in this thread is saying that this comes as no surprise, and that is certainly true. But the thing is, a lot of management types do know this already but they simply don't care for two reasons:
They care more about leverage/control over employees than they do about actual good work being done. You cannot understate at all how important employee control can be for managers and how seriously they're willing to destroy their own business to keep this kind of power.
RTO is basically a layoff program. As much as I love working remotely, it's very important to keep in mind that remote workers are the first ones that will get laid off when the business wants to cut back - purely because of how easy it is to do. They can just mandate RTO without actually calling it a layoff and know many workers will outright quit, and the business won't have to comply with whatever local regulations are in place around layoffs. Still, this shouldn't sound like comfort for employees that do work in the office - there's a good chance that once RTO is in place, another round of layoffs will strike when the company doesn't meet its cut targets. So any time a business announces return to office, it means that there's a good chance that layoffs will follow too.
tl;dr: Managers knew this would happen all along too - it was just a trade they were very willing to make.