I believe that the USC team came together to win the Rose Bowl in honor of Joe McKnight. He was a beloved former player of USC and was inspirational to many of the current players. One of the current team members even wore his jersey number in remembrance. His unfortunate passing helped inspire the team to a victory.
Yes, the emotions of dealing with Joe Mcnight's death helped USC win, because they played with a purpose. It is not uncommon for a person to find something positive that comes out of a tragedy. Then they use the experience as inspiration to come back and perform well. This is what happened to USC.
USC won a hard fought bowl football game, because of talented players and coaches, a season of hard work and a little bit of luck. In college football, any team is capable of winning in any game. Therefore, part of the reason a team wins a game is simply due to the luck of the game. In short, Joe McKnight's death did not help USC win.
USC's victory in the Rose Bowl was not just a matter of emotionally charged playing. They didn't get to the Rose Bowl by performing poorly. USC was considered a top team this year, and they played like one. Penn State fought hard and kept up closely, but in the end USC turned out to be the better team in that game. It's about physical strength and endurance and smart plays. End of story.