YouTube complicated things by having the dislike button double as a literal "I don't like this" and an "I don't want to be recommended videos like this in the future." When you dislike a video, it stamps it with a public seal of disapproval, even if you're just trying to avoid a recommended piece of music on YouTube Music.
It's a clunky, confusing UX that gave rise to the inevitable highly upvoted "Who in the world would dislike this?" threads on so many popular videos.
I've seen random harmless videos (bit of classical music for instance) with many dislikes.
Same with Facebook btw. They should never have added anything over a mere "Like".