I understand his play because of your play. He put you on a hand that didn't hit squat on the flop, turn, or river. He figured that you missed and his bet would push you off the hand. You didn't show ANY strength post flop with your hand. He checked into you on the flop to see what you did. Your check told him "I have nothing." He bet the turn and you called. He put you on something with big cards, but no pair. The river acted as a scare card. He figured you would consider him to have AJ and you would be beat and fold. Unfortunately for him you had AA and rolled him perfectly. Great win.