Deng missed all his shots in the 4th quarter of most of the games. As the series progresses, and you're asked to guard James, the most physical player in basketball, 1 on 1, that takes the lift completely out of your legs. They didn't choke, they just didn't have the talent. Get over it. The Bulls don't have the roster to win an NBA title.
Miami was just getting warmed up too. Notice how different everything was this year for them after 1 complete year together. They have 2 of the top 5 players in the league as far as I'm concerned and Rose is the only superstar on the Bulls and that's not enough in today's star-driven league.