Imagine two people walk past you on the street. One says "hi" and smiles. The other smears themselves with peanut butter and starts clucking like a chicken and saluting Hitler. Which one maximizes engagement?

Which one would the social media algorithms promote?

I credit algorithmic timelines as one of the primary factors in today's hyper-polarization. Twitter was one of the more influential ones, especially when coupled with a short character limit that prohibits deep discourse and as others have mentioned a lack of comment threads or other tools to organize ideas. The whole thing promote vapid sound bite meme-think, which best fits fanaticism and trolling.

Facebook and YouTube are the other big mass-lobotomizing engines. The mechanism is largely the same-- promoting things that maximize engagement which means the most inflammatory or ridiculous ideas.