Trying to give Trump the benefit of the doubt here, because I don't believe he really had an idea of the depth or the ferocity of the opposition. To be sure, Trump really didn't have a plan to drain the swamp, or much assistance. And he had to put together an administration while his predecessor was trying very hard to sabotage him, and using the resources of the federal government to do it.
I think the best we can hope for from Trump is that he is the one the gets the ball rolling. For better or worse, it was his personality that enabled him to break through the massive bureaucratic state. It will take another with some finesse and knowledge to do the rest of the job.
The reason I'm confident of all this is that the Trump administration has gone to great lengths to play everything according to the rule of law. You saw clear evidence of this in Barr's work to bring the Mueller investigation to a close (i.e., he has done EXACTLY what the law and U.S. Justice Dept. regulations require). For all his flaws, Jeff Sessions operated the same way.