Its funny cuz if he never left in 04, he would probably be as big if not bigger than Cena. Funny thing is his entrance video was from 04....he is not as big.
He probably got a very lucrative deal and a small amount of dates. Place sure did erupt when he came out tho-
I don't know the EXACT details of his UFC contract, but it was a sweet deal, and a major bonus is that he didn't have to constantly be on the road like when working for Vince.