Another reason someone could be banned in this situation (having an abandoned account that hasn't been used in years) is if they break a *different* rule on their active account, prompting staff to investigate them. Could be something like harassment, bigotry, inappropriate content, making callouts, or botting. I feel like this is what happened to hyrultia recently: lots of reports sent in about the callout post -> staff looked closer -> found multiple accounts -> banned for multi-ing.