Have you ever seen the posts? Some relatives comment on them so they show up on my feed, but the post will be something like "do you like dogs or cats better?" And my aunt and 10 million other people will make a post just saying "cat" or "dog"
It's sort of weird to have watched the target demographic switch from college kids to everyone's older aunts and uncles. We went from "you should know better than to post that picture" to "you should know better than to engage with that order of operations question".
To propagate (show up on more feeds), they need people to interact with it. So successful content will be that that best drives interaction, and I guess comments still weigh more heavily than likes?
Consequently, Facebook itself is a brute force algorithm for discovering the more virulently memetic content and phrasing.
Facebook really ruined the opinion I had of my relatives because of that kind of stuff.
Man, you taught me how to fish but look at you now, jumping on every bait thrown at you...