It was a world where Dean and Sam never existed, so he never bonded with them. He was loyal to Michael, who had taken over the world after the Apocalypse and was exterminating humanity. That Castiel helped him and interrogated the resistance.

[ Maybe evil was too strong a word but Jack has a tendency to think in black and white terms sometimes. He often uses that dichotomy for herself, whether he's good or evil, and he struggles with the nuances in the middle, even if it's where he truly belongs. He's still afraid of being like Lucifer. ]

He didn't have our family. That must have made the difference.