They intentionally designed it to suck people's time. It's a black box, but it seems to keep track of aggregate crossover interest somehow, then throw those crossover interest videos at you.

Which, unintentionally, helps feed the pipeline.

There were some pro publica articles about it, and I remember a software engineer who worked on it anonymously spoke about how it's designed to keep people on the site, and how that has a side effect of radicalizing the disaffected.