I think he was naive in not recognizing the obstruction the republicans would throw at this issue, nor the apathy of the average citizen towards it, thus allowing the republicans to be successful in their obstruction.

I really have no idea why we can't at least try the prisoners that can clearly be convicted in court, and keep them in super max in the US for their sentences. I find the resistance to this approach, by many in the US, completely baffling.

But the thorny issue is what do you do with prisoners who you're "pretty sure" are "bad actors" so you can't release them without political fallout (due to the expectation that they will continue to wage war on the US), but you also don't have sufficient hard evidence to convict them in court.

Part of the problem is that this is/was a war against non-state organization(s). Is the war over? Not really, I think most Americans would say. The name of the "enemy" has changed from Al-Qaeda to ISIS (or ISIL or DAESH depending who's speaking) but there's a strong argument that it is still essentially the same group of actors.

Okay, all that said, I think you HAVE to come up with a way to deal with the unconvictable prisoners so you can close the detention facility at Gitmo. Because the current situation causes more damage than what these relatively few people would probably do if released. On the other hand, at this point the horse is long out of the barn. You close Gitmo now, it doesn't reverse the damage already done. But you have to do it anyway, because it's the human thing to do. Eventually the stain will fade. It will take awhile, but the fading can't even start until you close the facility.