Infinite scrolling + algorithmic ads. That's how Facebook, Instagram, and Tiktok all make their money. You get way more ad impressions per hour than from people who click on links and read / participate in discussions (which is what Old Reddit is all about). Young social media addicts can scroll hundreds of ads per hour because they scroll so fast.
Except that Facebook has a rather nasty problem where friend-based social media is a soft monopoly (which they try very hard to enforce https://news.ycombinator.com/item?id=4151433) and its CEO already has a bad reputation https://news.ycombinator.com/item?id=1692122 and the product does not work on top of that (people miss messages, message requests, and posts, all the time)
"Addictive business model" is one thing. It's annoying, we should highly discourage it, but - some are worse than others
