Trump's primary appeal in my opinion WVPATX was to folks who were abandoned and betrayed by their elected representatives.
They didn't get to vote on the ACA it was forced on them, they don't approve of the massive deficit spending or waste of their hard earned money, they had no say when businesses closed up and moved away...then none came in to either replace the jobs or offers new & better ones, they saw illegal immigrants pouring across our boarder and eventually collecting social services needed by Americans displaced or economically struggling, they saw respect for us overseas, our Police, or other institutions like Marriage and Faith eroding, attacked & impugned, and they didn't see anyone speaking out against any of this or even upset by it until Trump came down that escalator in New York city last Summer and started talking about how all of this stuff just had everyone pissed off and needed to stop.
He wasn't seen as a part of those problems, and even if his solutions (wall, taxing outsourcing companies, beating Isis, etc) may not work, to many folks he was at least expressing their frustrations so they were willing to look past all of his other faults in order to see something finally being done about all of these things.
Then the Media compounded their frustrations by absolutely looking the other way when all of the stench of Clinton's and Dem's corruption came out, while they (Media) spent all of their time ganging up on Trump so everyone eventually just tuned them out. It didn't matter what Trump said, didn't matter what he did, they'd all had it with the Media's bias and as a result just totally ignored them.
I know this is an oversimplification, but in a nutshell it explains a great deal of why Trump has the Left now absolutely flummoxed and the political establishment absolutely terrified.