The official reason is report spamming. They had three warnings. didnt respond to any of them then when they had a chance to state their case when moderators were decided if action should be taken they just responded rudely.
There quite a few unofficial reasons that wouldnt have gotten him banned themselves but is against the spirit of the server. Just him starting trouble with people every single day almost intentionally. So no one is all that eager to dish out a fourth chance to him.