I think the whole show is about PJ being smarter tha everyone else. The thing is that, as far as we know, RJ is prooving to be the mastermind of the show, so even if PJ unmasks one of these 3 suspects I would still have the feeling that RJ is the smartest one.

In my opinion, for the show to be complete, PJ needs to set up RJ before catching him up, not just gathering the 5 suspects in a room, because anyone could do that. So I think PJ clearly knows none of the 5 suspects is RJ, and the whole bomb thing is part of PJ plan to set up RJ.