There is no "Powers That Be!". That's my whole point. Obama didn't do it because 1) he realized his entire presidency would be devoted on an uphill slog to better the lives of a couple hundred people, and 2) there was no simple answer as to where to put them. You can view the world through an us against them perspective, or you can actually try to understand how all the little bits of it interact with each other.
The simple answer is to let them go. You don't have to let them go in USA. If you can't bribe some Pacific island to take them along with all the Uyghurs, then release them in the benighted desert wasteland from where you kidnapped them. If the nominal government of said wasteland doesn't want them, use some of that good old CIA ingenuity to smuggle them in anyway. What better use of "Special Forces", than to fix previous screw-ups that used Special Forces?
The way to avoid "an uphill slog" is to just do it, via executive order. Obama knew about executive orders; he signed thousands of them while in office. That's a big reason why his successor has had such fun: while laws can only be changed by new laws, executive orders can be changed by new executive orders. Trump has staff whose only job is cataloging executive orders to overturn.
"National security experts" will tell us that the few hundred poor bastards we still have in the hole are some sort of existential threat to us a decade after we kidnapped them, but they are lying as usual. We are vulnerable to actual vulnerabilities, not random people with adverse sentiments. To lock up everyone who hates USA or the horrible things that USA does, we'd have to lock up about a billion people. To change the world, we must change ourselves.
Speaking more generally, this sclerotic way of thinking is why a cretin like Trump can get so deep inside the OODA loop of his political opponents. When they say "we just can't", it's because they can't find a lobbyist or think tank ghoul to tell them they can. When one considers all the truly awful things various politicians have decided they could do, it's a bit sickening.
