He is arrogant beyond what I have ever seen in the humans I have known (and he's done absolutely nothing to have earned it).
I don't doubt for a moment that he's mentally ill (including but not limited to psychopathic narcissism)...but there is something beyond even that.
I think he's cut a deal with the Devil.
Whether such a thing is possible or he only believes it is possible seems to be irrelevant. He appears to believe he is on a cosmic mission...and it is clearly not a mission sponsored by the God of Israel.;-)
If he is not the Anti-Christ he surely is the Anti-Reagan!