Why do you think? Enragement = engagement. You could generously assume that it's users optimizing for posts that get them likes/karma/whatever, or ungenerously assume that the platform itself is gaming engagement via AI or bots, but the effect is the same and it's pervasive. The only out is finding tiny communities that are still communities, and praying they don't grow.

Everyone saw the Facebook model and adopted it. It's why Reddit has the valuation it does (and why it's still insane to me people intentionally use it as a recommendation or information tool).