I don't know for sure, of course, since I don't know him - but, from all the interviews I've seen of him where the conversations were variable and unscripted, he has a very broad but also deep knowledge. I'm convinced that he's a voracious reader.
On a tangential note:
Over the years, many people have asked me how I know so many things... and I always give them the same answer: because I wanted to, so I put time into making it be that way. That's it.
While I feel that I should recognise that being reasonably gifted has likely benefited me here, there are _many_ people considerably cleverer than me!
I take pains to attempt to drive home the central point, which is that I believe it's the _attitude_ that matters the most of the two.
Just because I might have had a easier time than many when learning _doesn't_ mean it was easy, or didn't consume a lot of time and effort! No.
I just thought it was important, so I did it. It requires effort. It was an investment.
It greatly irritates me that many jump to the conclusion that some talent negates all the hard work that it required - and still requires. Learning never ends - or, it shouldn't!
I think most people are considerably more capable than they think - they often just don't try.