The most recent online mob I can think of was started by a guy named Jeremy, attacking a girl for wearing a Chinese dress as "cultural appropriation". He didn't want anonymity; he revelled in being known as the instigator, even giving interviews to the press. So I don't think that anonymity is the real root cause of online mobbing.
https://www.bbc.co.uk/news/blogs-trending-43947959
Jeremy by the way is an English name of Biblical origin: https://en.wikipedia.org/wiki/Jeremy_(name)