Rollins has run the show for a long time now, possibly since the beginning. He is the architect. He never got the respect he deserved, that was reserved for Reigns, the idiot muscle of the group. Rollins got sick of it so joined with Evolution, because Triple H knows who ran the shield, knows brain is better than brawn what with being the cerebral assassin and the game, and he will give him his due. This makes sense, especially if evolution can beat the shield sans rollins. That would prove without a doubt that Rollins was the main man. /kayfabe
I'm only annoyed because I wanted them to enter the Money in the Bank match and split there. I figure that would make more sense and have better timing with building tensions and rivalries back up in the group, with Rollins antagonizing the others subtly.