I realize Milbank's example of a Trump supporter saying “I guess I always just thought that it [Obamacare] would be there. I was thinking that once it was made into a law that it could not be changed" is just one example and not necessarily representative of the majority of Trump supporters. 
Given that, the general principle is that, as Trump supporters have said, "He's the President, he can do whatever he wants". 
It reminds me of those who might find a new partner that "knows their mind" and "takes charge" who later lament they are not listened to and taken advantage of. 
We'll see.