The only explanation for getting rid of dislike count that makes sense to me is to make big brands happy as their videos can't be made to look bad with a high dislike count and they can't be "dislike bombed" for things that may be unrelated to the content (eg the recent Activision-Blizzard scandals). Why? Because in every other way (and every way for the viewer), this makes Youtube worse. So it's a hell of a price to…
They were a signal or message that the message (but not the quality) was not approved.
Dislikes were being used as a form of critique of the content. They were a kind of mob/crowd behaviour than a personal like/dislike.
The YouTubers were both marginalised people, those waging culture war stuff and corporations.
By removing the crowd mob behaviour they also removed the intended crowd sourced recomendation system.