"...the hopelessly immature Donald Trump ..."

I think that statement right there is the key to  the whole Trump thing.  Trump is a guy who really has no idea what to do about much of anything so he remains in thrall to those who can manipulate his simplistic intellect.  Bannon for one is a master at it.  There are the Mercers, of course, and certainly Adelson.  Trump basically just lunges from one tweeted thought to the next.  Sometimes he speaks with a modicum of fluency but that is only because he is reading from some script.  Trump is not a Republican - - he's a Trumpian and nothing more.