It's probably due to a more recent change, IE, focusing on features over stability. Or, it could be that there was some turnover in ops and someone who was a hawk about stability isn't there.
If I were to bet, there's probably a product manager or other leader who's just gung-ho on new features and loosing track of who their customers are and what their needs are.
IMO, it's probably a combination of factors. I get the feeling GitHub has no clear leadership by anybody who actually USES it. The priorities internally were almost certainly "get onto azure, shove copilot/AI down everybody's throat, and other generic "product driven" initiatives. The user-hostile move to react was done in a way that broke browser back-button functionality, especially in Pull Requests.
They don't/didn't care because what are you going to do?
On one hand, the free users shouldn't complain too much, though I get their anger. But the place I work is an enterprise paying customer and this is bullshit.