This feels like one of those changes where they already decided to do it and used an experiment to justify their decision. The binary choice between showing only raw dislikes or no dislikes as well tilts the table towards an extreme change.

There's lots of interesting design choices they could have made of not encouraging dislike storms while still giving valuable info to viewers like highlighting if any video has an unusually high dislike to like ratio or attaching comments to dislikes and highlighting highly upvoted reasons why certain people are choosing to dislike a video etc.