I had a few alt accounts, they were all banned and I wasn’t able to make a new account with existing emails.

I assume, with no evidence, that they just used the same data tracking for ads, to enforce the ban. I think Meta turned on the real banning tech during a panic in Covid iirc

Their ban system is really hard to get around. They use a massive amount of different signals to try to detect anyone trying to get around a ban.

(Reddit has two forms of bans, shadowbans and permabans, both have essentially the same effect)