In the end Boston's stupidity did them in. The Heat built that big lead and never gave it up because the Celtics were too stubborn to try something else besides drive and kick 3-pointers.
They started off shooting something like 3-25 from 3-point range before they finally heated up just a little in the 2nd half, but by then Miami had already built a nice cushion thanks to all those Boston bricks.
I don't understand why some of these teams hate taking mid-range jumpers. When the Heat went into a zone defense Horford passed up at least wide 8 WIDE open 10-15 foot jumpers from the paint area. Instead of catching and shooting he'd either dribble himself into trouble or kick it out to a teammate for a 3-point attempt that they'd brick. He wasn't the only Celtic passing up good looks from mid-range. It was if they all took a blood oath to avoid mid-range shots at all costs.
If they'd have taken those easier shots instead of settling for threes, the Heat probably don't build that massive 1st half lead.
In the end I'm glad the Heat won because I hate seeing incompetence be rewarded.