The protests were only really widespread in late November, after the Urumqi fire, and then China embraced COVID in like the first week of December. A few policies stuck around and there was a slower rollback of those, but they did literally go from "quarantine camps for close contacts" to "everybody catch it, don't even bother testing" in the space of about two weeks.
Don't really know how much more "abrupt" it could have gone.
Effect of covid maybe? The lockdown was a pretty dire time but I've never seen neighbourly solidarity like I did in my xiaoqu over those three months.