That's what you call an old-fashioned swerve.
A few weeks ago, former Daily Show host Jon Stewart was announced as the guest host for this year's SummerSlam. Now, Seth Rollins and Stewart have already had some altercations in the past with Rollins hijacking the Daily Show a few months back. Knowing that, it would seem logical that Stewart would get involved somehow and when the referee was knocked out during the WWE/US Championship match, Stewart headed to the ring with a chair.
At first, Stewart seemed conflicted on his decision, but finally ended up hitting Cena across the head with the chair, allowing Rollins to get the pinfall. Stewart was seen leaving the arena after the attack with his son.
Jon Stewart just turned heel at SummerSlam, taking out John Cena w chair. pic.twitter.com/KaRG8qa7v9— Jimmy Traina (@JimmyTraina) August 24, 2015
His pinfall over Cena makes Rollins the first WWE and US Champion.