I suspect there's a simple explanation. Sometimes people go on massive subject binges and there's likely certain videos that are more likely to trigger this tha

I suspect there's a simple explanation. Sometimes people go on massive subject binges and there's likely certain videos that are more likely to trigger this than others. If you watched one the youtube algorithm is basically asking if you'd like to binge the rest because a lot of other people did. In terms of watch time and retention on site I imagine those binges are gold hence why they've ended up being optimised for.