@Azzuri0 Well, as I said, Airbnb wll not tell you why they removed the account, and that message you got about them violating the terms of service would make me quite wary, as Airbnb does not delete guest accounts even for some pretty seriously objectionable behavior. And perhaps their last stay was bad, but the review didn't appear or was removed or the host didn't leave one. It's also a possibility that it was just an Airbnb glitch. What I would do is contact Airbnb to tell them that the guest IBed under a different account and ask them if they can assure you that it is okay for you to accept this reservation. You could also ask the guests if they have any idea why this would would have happened.
"Seeming" normal through messages, while I understand what you mean, may not be an accurate take on whether guests may present a problem.