I think there are some intersections of interest that make the algorithm hypothesize that you're a certain kind of person. Like if you watch a lot of strength training content, and then you watch one lecture on Heidegger, YouTube is like, oh, we finally figured this guy out, he's a white supremacist or at the very least a gun nut. But if I watch a video about cupcakes, I'll only get a few suggestions about baking, not any associated interests, because cupcakes don't combine with any of my other interests to trigger a stereotype.