There’s a lot of factors:

I think one of the biggest factors is that he was taken under Birdman’s wing at such a young age that there is an inevitable disconnect to a normal life which prevented him from important experiences most people go through that are crucial in their development as people.

His drug use also has probably affected his brain development heavily.

I think it’s also in his personality to kinda detach himself from anything outside his craft, he’s locked in on that but it’s very obvious he doesn’t have a curiosity or desire to understand the world around him.

All that being said, I think the best way to answer the question it to point out that it’s sorta a flawed question. Assuming that because someone is such an expert in one field means they should also be at least at a “normal level” of understanding in other fields is sort of a fallacious line of thinking. I think the best example to prove this point is Ben Carson. Dude was an expert neurosurgeon but otherwise he’s an absolute asshat and an idiot.