CM Punk started his WWE main roster career back in 2006 and the promotion had big plans for him ever since he joined. Soon after joining the promotion, he won the ECW World Championship. ECW was restarted by WWE during the time as a parallel brand besides Smackdown and RAW. Punk started working in the newly reopened ECW following his debut.
In 2008 WWE decided to push him on to the main event level. He went on to win the Money in the Bank ladder match in 2008 at Wrestlemania XXIV and later cashed it in on Edge. Bruce Pritchard recently looked back at this cash in and explained why it was internally quite controversial. Speaking on his Something to Wrestle With Podcast recently, he revealed the following;

Wrestling Legend Claims CM Punk’s 2008 MITB Cash In Was Internally Controversial
“Very controversial (CM Punk cashing in Money in the Bank on Edge). It was controversial because I don’t think that Punk had a lot of people in the locker room that were really pro-Punk. He’s a polarizing figure. I thought, if he’s that polarizing in the locker room then, what’s the general audience feel about him? And I really felt the general audience was intrigued.
“He was different and there was something about Punk, especially at that time… it was a groundswell. People were getting behind him. I thought then, I think now, later on when he did the whole X Division, I thought that he was a much better heel, a natural heel. The idea at the time was for him to eventually turn heel. The way that they did it, that was after I was gone, I thought was superb.

CM Punk Won Back To Back Two MITB Matches
“I thought it was really good for him but again, in an effort to shake things up, you wanna see surprise on people’s faces? You wanna see genuine reactions? Have a camera backstage when Punk won the title. There were those that were like, ‘What the hell are you doing?’ There were those who were happy for him and again, it was a moment that no one was going to call, and I thought it was a good one.
“Hopefully, if you listen to the beginning of this show, you heard me talk about and praise CM Punk and talk about how he was misunderstood and how people felt about him and the fact that I thought that we just needed to explain who the hell he was… and people have a habit of you look at somebody and immediately form an opinion of who they are by the way they look and you can’t do that.

“That just doesn’t work in life, and I think Punk was a victim of that… The interactions that I had with Punk during that time were all good and we had great discussions. Look man, we had philosophical differences at times that we were able to talk out and that’s why I learned so much about him and figured out that, wait a minute, this guy’s just misunderstood. “
CM Punk became the first and only WWE star to win two back to back Money in the Bank ladder matches as he went on to win the Money in the Bank ladder match of 2009 as well. His actual main event push started after his 2009 Money in the Bank win and he went on to become one of the biggest stars of the promotion.
H/T to POST Wrestling