спойлер
“Again I think that Cas is trying to pay some kind
of penance. He’s trying to make up for the wrong that he’s done before.
[…] The big question is why did Cas abandon Dean? […] Basically, yeah,
he left Dean because he wanted to try to keep him safe. And [Cas] being
around is actually a liability in Purgatory.”
Миша думает что Кас в чистилище пытается расплатится за свои грехи. И он оставил Дина ради его же безопасности.