I don't have any proof but I believe it's because of all the stories in the press about scary "alt-right/conspiracy rabbit-holes" and how something _must_ be do

I don't have any proof but I believe it's because of all the stories in the press about scary "alt-right/conspiracy rabbit-holes" and how something _must_ be done. A YT rabbit-hole is exactly how the product should work; you watched these videos so I'll show you closely related videos because you're more likely to stay on the site and generate ad revenue.