A good piece from Mother Jones on what Trump and Bannon are up to with this ban. Basically, they think this will galvanize Middle America to their side.
The only thing I would add is that the Trumpsters are also trying to discredit the Left by claiming Obama did the same thing, and no one complained.
While the Obama administration did stop processing Iraqi refugee applications for 6 months while they tightened measures, they didn’t stop Iraqis of all visa classes from coming, nor can I find any evidence that people in transit were abruptly denied entry by Obama’s Order, like they have been by Trump.
Updated: And here is another theory as to what Bannon and Trump are up to. It’s an attempt to undermine the judiciary: