Random, sarcastic, nerdy.
Cas didn’t give up his grace. It was stolen from him. We always assumed it would be his choice for some sacrificial reason. I feel like this is the writer’s way of mind fucking us. For me that was the most shocking part of the episode, that Cas wasn’t given a choice of falling. Ow.
Crowley gets cured, but he’s still a demon, he has a conscious to go with his powers, so he just lives for a really long time. And 500 years in the future, he’s no longer going by “Crowley” and instead of being the King of Hell, now he’s a sad little king of a sad little hill. He goes by Badger, and he does underhanded dealings with space cowboys.
But first he has to go though his Angel/Angelus phase…