I'm going to start this article off by saying that I have zero information to back this up, but it is my theory so hear me out. Shaq hurts his wrist and needs a few weeks to get better. The Cavs, knowing that they are going to run away with the best record in the East and most likely the whole NBA, decide to have Shaq continue to sit and spend his time getting into shape. He most likely was told that they need him to win against the Lakers but that if he gets hurt or is not in shape then they won't be able to. Shaq has gone from looking like he's a burrito away from being Oliver Miller to looking like he dropped a good 20 or 30 lbs.
Like I said, I have no news source to back this up, but why not get Shaq into shape and fully healthy when you need him most: in the postseason.