We call him delusional cause he has lost all humility. He is utterly convinced that he discovered the underlying mechanism of literally everything from physics to eceonomics. Delusion of grandeur is a well-known psychological condition, and no matter what you think of the science, it's hard to argue that Wolfram doesn't have it.
Why can't he just say: "hey I've got this idea, it's crazy, but you know what? I am going to pursue it and see where it leads, anyone wants to join?" Noone would be annoyed by that.
Whether being delusional affects the way you work, I would tend to think so, but you can think otherwise...