Haven't read the whole thread, but new studies are showing WFH is lower productivity than in office, in contrast to the initial studies that suggested it was better to wfh. That's part of what is driving these changes.
Also, I think it depends A TON on the nature of the job. If you are doing individual project work vs constant working in a group. Aslo depends on communication complexity required. If you have simple and clean handoffs, wfh is easier. More nuanced stuff is harder.
The other factor that's important is company cohesion. If you have half your jobs wfh, but the other half must come in, it can definitely seem unfair that some people have to come in and others don't. Even if it makes sense (e.g. warehouse workers vs accountants) it can still cause a lot of challenges to be fair to everyone.
All that said, if you got hired for 100% wfh, and they are changing the rules... either vote with your feet, or ask for a raise and/or more PTO to make up for the increased time and commute cost. If they want to change the rules, then you can try to change them too.