In his case, if he does decided to create other accounts (or already operates them), I guess eventually he will be caught out because if a new or low ranked member decided to continuously post about making unlimited money and posted links to their website, I think members will link the accounts

I do not know about the other troll that announced they were leaving only to return with another account but this seems to be a new tactic they employ either to seek attention or seek sympathy.
Usually such trolls don't just leave the forum. I am pretty sure there is some Alt somewhere trying to keep a low profile so that they can't be detected. There was some other troll who about a month or two ago announced that he was leaving the forum for good, only to turn up with another stupid Alt account and most people haven't noticed it yet

Some of them have mental challenges. It's why I don't bother so much with them.