Maybe it was low hanging fruit? Removing the counter might eliminate easy coordination of distributed automated attacks. It could make botnet brigading less nuanced, and possibly easier to detect and mitigate. It also disincentivizes human brigading by removing context.

Channels get shadow banned by activists through manipulation of automatic moderation. This required keeping the activity under the threshold needed to bring a human in the loop. It's been a while, but there are guides on dark web forums on targeted harassment and manipulation of auto moderation of various platforms.

It's always frustrating to see non techy creators wail and gnash their teeth about being banned or harassed by a platform, when it's a million times more likely that a small group of dickheads manipulated automated rules using downvote and channel reporting features.

Not sure why captcha or other barriers aren't required for the use of abusable functions on social media, that's always seemed very user hostile.

It very well could be the mitigation of coordinated botnet attacks and the like. But the other possibility is the removal of a very easy method of showing disapproval. Youtube has been pushing more MSM sources on the platform and they don't want to harm their brand/product. Check out this Fauci Documentary trailer (with the extension, hehe) https://www.youtube.com/watch?v=zJYnE1xWdZI

And the above example also plays into the political angle of removing the dislike button. ie antivaxx narrative.

People will now be able to perfectly manipulate their audience by deleting every unwanted comment and hiding behind the fact that dislikes not being present is not their fault. I'd argue that viewers need more protection than creators.