The Miami Heat needed to add another big man in their power rotation. You specifically note that part of it, the “power”, because they’ve actually added or have guys in their big man rotation that just don’t quite give them that something they’re missing.
Trevor Ariza is a stretch-4 type, but plays mostly along the perimeter, lacking that girth and physicality you might need on the inside and at the rim on both sides.
Nemanja Bjelica is also a four-man, however, he is far more finesse than brute of any kind. Precious Achiuwa could develop into that, with weight room activity and more overall work on his game, but he’s a quick, wiry strong, and slashing rebounder right now.
The Miami Heat needed a guy with size who can come into the game and play with physicality on both sides of the ball. They needed a guy who can help establish them in the paint with an easy bucket or two, perhaps, while also being able to plug him near the basket for rim protection, be that with Bam on the floor or without.
Dewayne Dedmon certainly fits that bill.