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.