Not necessarily. Maybe he considers himself SO powerful that it doesn't matter what any of us think of his decisions. After all, in his mind he WON, so he thinks he can do whatever he wants.
From WaPo: "The tactic was also used by the Bush administration when it wanted to stop various proceedings in Guantanamo. The Pentagon has dismissed without prejudice charges in six cases, and reinstated them later in three of those cases."
I think those here thinking he's just letting this guy go because he wants everybody to know he hates America and the military and loves terrorists need to take a chill pill. He's not that stupid.