The Mavs won because they had better OFFENSE!!! The Mavs play great D, but in the end the Heat couldn't keep up scoring wise. The Heat can't play any better defense, it was GREAT Mavs offense that won this title. So I don't wanna hear that you can't win with a good defense and a great offense. You don't have to have the #1 defense to win a championship. This isn't to say that defense isn't important, we all know it is, so don't go there. I'm just saying that you want a team that is capable of getting it done in more than one way. The Heat have never been a very good offensive team. They tended to beat teams with their defense getting steals and scoring easy buckets on the break. With the Mavs they run such good offense, that there weren't a lot of those easy fastbreak buckets that the Heat usually live off of.
The Mavs spread the floor and passed so well that it stretched the limits of the Heats great defensive quickness. The Heat didn't have an answer for the Mavs best player defensively, cuz the Mavs had enough real threats on the floor to give him room to work against single coverage or a late help defender. The Heat offense stinks. If not for the great individual talents of Lebron and Wade their offense wouldn't be that effective. The Mavs were deeper and had more answers for the Heat defense than any team they faced in the East.