#3. He is at the peak of his career
There's no doubt in the fact that Rollins' in-ring abilities have always been prestige as he managed to gain enough experience during his tenure on the independent scene. He made a name for himself in ROH before doing the same in WWE with his run on NXT and being a member of The Shield.
But it's the fact that Rollins has officially found himself as a character, which is the most important aspect in him being at the peak of his career. Sure, Rollins has been the world champion before and you could make the case that he was at his peak whilst being part of The Authority- but that was Rollins whilst being a heel. And he was constantly overshadowed by Triple H & Stephanie McMahon as Rollins wasn't able to thrive on his own. There is no doubt that his credibility was being diminished whilst being aligned with Hunter & Stephanie.
As a member of The Shield, Rollins played the role of The Architect whilst Ambrose was clearly the lunatic- along with Reigns being the destroyer of The Shield. But despite Rollins standing out whilst being part of the trio, the focus was always on Roman Reigns until Rollins had stabbed The Shield in the back to become a member of The Authority.
Rollins is clearly at his best when he plays the role of a babyface as he is clearly making movements on his own, and despite struggling to adapt to the alignment when he first turned face- The Architect has managed to develop his character into something truly special.