Didn't look that closely, but my guess is that
1. Your opponent bought treasures, which anti-synergizes with Poor House. Your Nobles buys gives you around the same buying power off Poor House. It's a bit less, but you get 2 VP + better cycling, so it works out to a net gain.
2. Early Jester probably helped as well, money off actions is really useful here to get more mileage off Poor Houses
3. Your Nobles didn't get hit by Jester until fairly late, whereas you got a decent amount of Victory card hits. You also never hit a Silver or Gold from what I saw, which is probably the worst hit you can get in this board.