Civil government is a mechanism of consent. Garland never got a hearing because the Republicans asserted they would not consent civilly to the historical mechanism. Obama could have appointed Garland through a couple-three different approaches, but doing so would have signaled that the consent that keeps government civil was eroding further.

It's a game of brinksmanship - how far are you willing to push the Jenga stack to get your way? With the Republicans daring Obama to knock it over, his choice was to prop up their bullshit brinksmanship. The Obama administration judged that governance of the United States was fragile and that the best path for the nation was to let the Republicans have their tantrum. I'm not sure I agree and I reckon this particular period of history will be studied for a long time... particularly when the next guy in the seat didn't realize he was paying Jenga.

There's literally nothing stopping Trump from issuing an executive order banning Muslims on a Friday afternoon. However, as has been amply demonstrated, it's not the cleanest, easiest way to go about it. Historically, presidents have understood the delicacy and nuance necessary to keep a three-headed representative democracy firing on all cylinders. Now, however, we're going to test the limits.