Hold on, let me get this straight: You think that someone who does what he does because he honestly believes he is doing god's work (because of a mental illness) is a dumbass?
Next you'll call John Nash fucking retarded for being afraid of men in red ties.
Nash was great in spite of his issues, not because of them; his work was a real, useful contribution to human knowledge, because (in contrast to this guy) he worked with the wider mathematical community, which then in turn later built on his work.
Being afraid of men in red ties is still a dumb thing to do, and won't make you a great mathematician. We romanticize the outsiders, but the great bulk of the mathematical edifice was constructed by relatively ordinary, well-adjusted people like Euler. If you want to be a great mathematician, it isn't Nash you should model yourself on.
Erdős was one of the greats, but emphasis on "one of". Again, it's easy to romanticize someone who's different, like a microcosm of orientalism. Erdős may even have been the best mathematician of his generation, but he wasn't head and shoulders above everyone else the way people sometimes seem to imply, and he wasn't (IMO, if the question even makes sense) the best of all time.
Next you'll call John Nash fucking retarded for being afraid of men in red ties.