Easy...its called poor booking and shit product.
Poor booking, indeed! In 4 Manias, Bryan went from pre-show match for the US title with Sheamus (which he lost) to a curtain-jerker World title match against Sheamus (which is supposed to be a 'main-event' match, since Sheamus won the Rumble and which he lost).
I kid you not. I went to pour my son some apple juice and, as I put the lid on his sippy cup, I hear Sheamus' music playing. I get back to the living room and Sheamus has the belt in his hands.
Last year, he has as meaningless tag team title defense with Kane. And now, he main-events WrestleMania and wins both WWE and World title belts.