John Cena had every reason to become the monster that Bray Wyatt wanted him to be and get himself disqualified to destroy his adversary, but he didn't. He hit his finisher twice and won fair and square, because he is John Cena.
If you're unfamiliar with Bray Wyatt, he's the best character that WWE has introduced in years. He leads a Louisiana bayou cult called the Wyatt Family and gives passionate promos in language that's equally cryptic and poetic. In real life, he was a Division I offensive lineman and he wrestles like you'd expect a Division I offensive lineman to wrestle. He's put on incredible matches with Daniel Bryan and The Shield coming into WrestleMania, and everything about his recent work suggested he was ready for the step up to the big time -- a WrestleMania match with John Cena.
I'm going to assume that you are not unfamiliar with John Cena if you are reading about professional wrestling. He's been the man on top of the industry for a decade. The story behind this match was that Cena's clean-cut babyface personality is all a lie and that Wyatt, a man destined to show everyone the real truth of the world, was going to expose that lie.
The characters played their part perfectly in getting that story across during the match. Bray started the match by kneeling in the center of the ring, telling Cena to end the match quickly. For every bit of offense Cena got in, Bray laughed in his face, enraging Cena further and leading him to bend the rules a bit. The referee even played his part by yelling at Cena to knock it off, and even convinced him not to use a chair at one point. The continuation of the outside of the ring story to the match was perfectly executed.
Well before the outcome of the match became obvious, it was very clear that Wyatt was being treated as a very significant opponent for Cena. He ate an Attitude Adjustment pretty early and Michael Cole didn't act like it was a big deal at all. He halfheartedly questioned if it was enough and wasn't shocked at all when Wyatt kicked out. Cole acted significantly more surprised when Cena managed to kick out of a Sister Abigail.
But at the end of the match, Cena did what Cena does. Bray looked to have another Sister Abigail locked in, but Cena countered, got Bray up for AA No. 2 and pinned the leader of The Family clean.