Because of the blow back from fox. That's why. Everyone was greeting him and welcoming back at the start, but then as soon as every rw commentator started calling him a traitor and his dad part of the taliban etc, then this happened.

John McCain, in february called for a deal to be made, then as soon as obame did it, he needs to be impeached. If you can't see the hypocrisy and politiking involved here, then you're deluded. Check out the twitter in that huffpost link to see how many people are tying themselves in knots to be against something they all wanted, right up until the time obama did it.