You don't put someone in the stockade for being an idiot. He was no traitor, just a moron. If someone else had wandered off, he would have likely joined the search. One factor that assured him leniency was the fact that Trump spent his time shooting off his mouth about the case. Had he never mentioned him and precudiced the system, Bergdahl would have likely served a sentence. Because Trump can't shut up, the defense has entered motions to make the sentence even less, which is lawful thing to do when the POTUS is more of an idiot than the convicted.