I suspect he didn't grow up. Dropped out of high school at 16, knew he was smart, never had any humbling experiences, etc, etc. Not at all to excuse his god awful behaviour.
Actually this makes a lot of sense, basically struck it rich as a child and never had to go through the normal social experiences that help define who we are and our values. Believes that money is what defines him and everything in the world can be solved by more of it.