This is why Rock won.
Cena winning in THIS match at THIS event in THIS town would have been a disaster, even if conventional wisdom says the younger guy who's sticking around should beat the Hollywood celebrity who isn't going to be around for months.
Cena can beat Rock at Summerslam or something and go over him once and for all, and it will be just fine. The setup for this Wrestlemania just didn't allow for Cena winning unless they were willing to accept the crowd shitting all over the "biggest main event in Wrestlemania history."