I haven't actually found David to be as egotistical as is sometimes said.
I suppose you read things according to your perceptions, but to me, when he speaks of the books he read as a child, his intelligence and so on...I just see that as someone trying to reassure the people he is trying to reach that he's not a total fool.
A bit like stating your credentials in an arena where some are simply charlatans.
I also appreciate the fact that he doesn't bad-mouth or attack anyone.