Dave, I think you may be making judgements on the persona that you see projected on the screen, confusing that with the man behind the programme. He acts the buffoon, the immature lad - because that's what people bought into. He is by all accounts, a very bloody intelligent and capable bloke.
That Top Gear was taken from an average BBC TV periodical into the phenomenon it became over a few years from circa 2001, was down to Clarkson and his Producer - not a fluke of the Beeb.
cheers