Earlier quoted context omitted.
I trust that the people felt his behaviour was awful. If they don't like working with him, they can switch jobs. Or even complain to higher ups and what not. What is not OK imo is this appeal to some imaginary "societal moral court" that should somehow punish the guy.
Why are you arguing that awful behaviour should have consequences for those it is direct at, rather than for the person who commits it?
It is a pretty normal thing that people don't get along with each other, for whatever reason. Just because one party goes public and frames the other as a horrible person, doesn't necessarily mean they really are.
If nobody who is disliked by somebody could become boss, there would only be very few candidates left.