His goal really changed the game. Before that the players and the crowd were all nervous and unsure. Then MLS stepped up and decided to finish them off. Liberated the entire stadium and lifted a ton of pressure off the team. Also wrecked the City morale and ensured there wasn't going to be a comeback.
We've had this done to us so many times over the last 5-10 years. Just when we're getting back into the game, someone pops up with a decisive goal that completely deflates the team.