The question is whether it's possible to simply be mistaken about having divine powers, without having an underlying mental disorder. And clearly the answer is 'yes;' and clearly this possibility has a higher prior probability than 'Jesus is Lord.' So neglecting the option is unconscionable, and is where the trilemma gets nearly all of its plausibility as an argument for Christianity.

Suppose a few really unlikely events happened, and caused everyone around you to think you were the messiah and/or divine. Would it be inconceivable, barring true insanity or deliberate deception, to come to think oneself the messiah and/or divine? Do you think that every psychic, every cult leader, is either (independently) insane or deliberately lying? It just ain't so; self-deception is stronger than that.