That last part seems to be somewhat in dispute - I suppose mostly because "directly" is rather ambiguous in these cases, and we never know what would have happened otherwise.

And you do realize how idiotic "he negotiated with the enemy" sounds as a reason for impeachment, yes?

Or maybe he just followed the long-standing military policy which, as moondog notes, his (domestic) enemies would just as strongly have defended if he had violated it, as they decry it now that he followed it.

Quote no. 1:

Rear Adm. John F. Kirby, the Pentagon spokesman, said that there was a larger matter at play: The American military does not leave soldiers behind. “When you’re in the Navy, and you go overboard, it doesn’t matter if you were pushed, fell or jumped,” he said. “We’re going to turn the ship around and pick you up.”

Quote no. 2, from Martin Dempsey, chairman of the Joint Chiefs of Staff:

In response to those of you interested in my personal judgments about the recovery of SGT Bowe Bergdahl, the questions about this particular soldier’s conduct are separate from our effort to recover ANY U.S. service member in enemy captivity. This was likely the last, best opportunity to free him. As for the circumstances of his capture, when he is able to provide them, we’ll learn the facts. Like any American, he is innocent until proven guilty. Our Army’s leaders will not look away from misconduct if it occurred. In the meantime, we will continue to care for him and his family. Finally, I want to thank those who for almost five years worked to find him, prepared to rescue him, and ultimately put themselves at risk to recover him.