The Shield is one of WWE's biggest factions and has long been seen as having given birth to three huge main eventers in Roman Reigns, Seth Rollins, and Jon Moxley aka Dean Ambrose.
CM Punk was on The Rich Eisen Show, talking about several things, including his upcoming WrestleMania match. He talked about how Roman Reigns and Seth Rollins were chosen and the Shield was put together along with Dean Ambrose, and he revealed the real idea behind it. He said that he wanted to elevate other stars to reach the massive heights of the main event in WWE so that he would have others to work with.
The entire reason behind the Shield was to create future main eventers. It's safe to say CM Punk's idea was a success, even if he was not attached to the group.
"In 2012, I was the champ, I was on what at the time was a historic run with the belt for 434 days, obviously shattered since then by Roman Reigns, since I've been gone. What I needed was guys to work with. I was always looking towards the future. Yeah, there's the now. There's the me, and there's Cena. But outside of that I would look at the landscape and would wonder, 'What do we need to do to get money talent in the position that I'm in now. How do I bring guys up? How do we elevate superstars?' So the idea of the Shield was that simple, I need guys to work with, for good or bad." [From 10:46 - 11:37]
He went on to say that it was funny that now it was Roman Reigns and Seth Rollins that he was facing at WrestleMania after all that.
CM Punk is the one behind the idea of the Shield, but instead of being what it was, they were supposed to be connected with him.
For whatever reason, this didn't happen, and they became their own faction, which in turn helped everyone involved.
Now, the stars, minus Ambrose, are going to face each other at WrestleMania.