I think there are two reasons you won.
1. Your opponent gained Curses more aggressively than you, including times where they gained Curses without much hope of drawing their sole Steward. Meanwhile, you chose to discard whenever you were tortured without a Steward, probably because your opponent went for the Conspirators instead of more Torturers like you said. This resulted in a 2-0 Curse split in your favor.
2. Your opponent got some really bad draws late in the game, and they were forced to break PPR because you would have won on piles otherwise.