Before Aizen could take out Ichigo he was shot in the back by some kind of Special Beam Cannon. But on closer inspection, this was actually a kido seal installed by our friend Urahara Kisuke! This was specially made to seal this newly transformed Aizen, and was placed on him during the middle of his transformation way back when. It only took control now because of Aizen’s weakened state. Basically like any sex craved ho, the Hougyoku is only attracted to the strong, and that isn’t Aizen anymore. With that Aizen is gone, disappearing in the middle of some crucifixes like an Evangelion angel.
Thanks Urahara for showing up after Aizen was practically dead. What if Ichigo didn’t show up, would you have just stood their and watched as Aizen destroyed the town? Either way, I wish Ichigo’s bad ass form lasted more than two chapters. And we all know that if he has the opportunity to whip it out again, it isn’t going to be as effective--according to Shonen Jump law.