My theory is that his physics and economics degree helps him to think technically and with a business mindset. Added that he reads widely and is talented.
In my opinion, the world will be a more interesting place if people learn to think like him.
No, it's mostly that
(a) he has the will to ventures in various fields
(b) he has the money (from his early ventures) to venture in various fields
(c) he hires people who know their stuff in those fields
He doesn't have to come up with anything resembling real innovation (a new technique or process) himself. He just have to give his stuff the general direction and push them towards it.
Having a technical and business background helps, but don't imagine any Tony Stark like lab research on the technical level done by him personally.