Bans and bullying

Been speaking to some mates who were members on this site.

Why are people banned without being provided a reason and their IP blacklisted?

Is retaining someones IP to block them not a breach of the GDPR if they have closed their account?

Already seen one post complaining about people joining using different usernames and WUMMERY, wouldnt be a problem if you maybe gave temp bans first? A warning? Then a ban and clearly provide reasons and an opportunity to put their case?

Seems like there are a few bullies on here myself and I've only been on here ten mins!