And truthfully, he never really was that over. They gave him EVERYTHING, and he couldn't ever turn it into raw "overness".
So tired of this claim. Punk's original following had a ton to do with the niche audience that adores the Indy guys. The same can be said for a number of guys such as Daniel Bryan, Seth Rollins, Dean Ambrose, AJ Styles and a number of the NXT guys...
But in the case of Punk - as well as Bryan (and Ambrose to a lesser degree) - their popularity with the niche audience grew to the mainstream level. No one can deny that Punk was the hottest figure in pro wrestling in the weeks following the 'pipe bomb' promo. At that point, a niche audience of fans weren't cheering for Punk because of his indy background. The vast majority of the fans were cheering him because he brought an electricity to MNR that hadn't been seen much since the Attitude Era. That promo reminded people that wrestling could be edgy at times, that the WWE was willing to bring a certain amount of reality back into its program.
But then what happened? They took everything people loved about Punk and used it to build up other guys. For example:
1) He got thrown into a program with Triple H and Kevin Nash. During the course of that program, he was beaten by Triple H... and laid out multiple times by Kevin Nash. The payoff? Triple H defeated Kevin Nash in a ladder match. Seriously... they took the most over guy on their roster and used it to build a feud between a 42-year old executive and his 52-year old best friend. And in case we weren't throwing enough cold water on Punk during this time, Punk - who had essentially ascended to mainstream status by calling the entire McMahon family (including Triple H) a bunch of morons - went on MNR and told Triple H that he considered him a friend. Hell, they had a tag team match together - which they lost...
2) Punk got over by saying and doing things that went against the authority. But with Punk basically siding with Triple H, the WWE needed a new anti-authority figure. Enter Miz and R-Truth. Two loose canons who ran roughshod on the WWE during these months. Not only did they defeat Triple H and Punk in a tag-team match during this period, but they also laid out CM Punk during his WWE Championship rematch. Did Punk ever get retribution on these guys? Nope... that was left to John Cena and The Rock who squashed them at Survivor Series.
3) With Triple H being fired by the board of directors, due to the Awesome Truth angle, and a new heel authority figure in place ... Punk was finally in place to challenge the authority as a face. From December through February, John Laurinaitis tried to screw Punk out of the title. While this wasn't the primary program in early 2012 --- Cena vs Kane headlined the two events prior to 'Mania --- it did have a good place on the card. The payoff? Well, once Cena was done wrestling main events against Kane, The Rock and Lesnar - he finally came to Punk's aid, standing up for him and taking down John Laurinaitis in the main event of Over the Limit.... Actually, cross that - Laurinaitis won with the help of the Big Show, which set-up the main event for No Way Out where Cena defeated Show to get Laurinaitis fired.
People just want to look at Punk's long title reign as evidence that the WWE was behind him, but were they? People wanted to see Punk take down Triple H, but instead Triple H went over on Punk - and not only that, but Punk became friends with him immediately after. Then people wanted to see Punk take down Nash, but instead, that job fell to Triple H. Then people wanted to see Punk take down Laurinaitis, but that job fell to Cena. The first half of his title run was a complete let down because the WWE refused to actually give the fans what they wanted. Triple H refused to play the villain and they refused to take Cena from the main event. That's why his heel run was necessary - because wrestling against Cena (and later, The Rock) - was the only way the WWE was going to let him defend the title in the main event.
But as for the original thread of this post --- Reigns is going over at WrestleMania. The WWE isn't going to put this guy in back-to-back main events and not let him go over at either. That would completely kill any chance he has of ever getting over. Legitimately, the only way he doesn't go over at 'Mania is if he's not in the main event. And since they spent the past 6 weeks building Triple H and Roman Reigns - and since Triple H has the WWE Title - it's just not plausible for the WWE go to with any other main event outside Triple H vs Reigns for the title.