Well, it's because the magic shoot a lot of 3s and allow/encourage other teams to follow suit. Their perimeter defense isn't that good so they sag off a lot, and also mostly always go under on pick and rolls. This opens up a lot of 3s for opposing teams and also their transition D isn't that great so they're oft out of position and give up 3s. However, most teams can't do this like the magic can where they have great shooters at 6 of the 8 players that actually hit the court and usually 4 at a time. Teams get sucked into playing the magic's style kinda like what the suns used to do. Also, the magic occasionally get DOMINATED on the glass as they really don't have anyone on the team who boxes out well. Howard is a great rebounder but still rarely boxes anyone out. Teams like the cavs, or even celtics without garnett who slow the pace, attack the glass hard, play good D, have plenty of random bigs to throw at howard (especially Big Z who can draw howard from the hoop with his shooting/passing ability), and with good penetrating guards really can give the magic fits.