>> people who kept posting as if nothing changed typically were extremely low-value posters

absolutely not, ... these were (and are) always there. instead it was Facebook management decisions choosing to amplify exactly this. Let's not blame a minority of (misguided) content creators for the shortcomings of Zuck and his sycophant senior managers.

As anti-Zuck as I am, I argue this is simply human nature. I've seen the same effect all across internet interactions, from Gamefaqs to 4 chan to Tumblr to Tiktok. controversial content will simply draw in more discussion (i.e. flamewars) than any other kind of contnet. sad content, happy content, funny content; it all falls to rage bait.

The only blame on Facebook's end is a failure to moderate and mitigate it. But at that point you ask if that would have simply pointed the controversy to the moderators (something also commonly seen).