The answer to how Trump has succeeded is really simple: He lies nonstop, and lying works. Sure, there are other factors in play—he tapped into and intensified a certain strain of profound proletarian resentment of liberal elites, and … well, that’s about it. But mostly, it’s the lies.
…And, to reiterate, Trump tells many such lies a day. He talks to the press two or three times a day most days, which probably adds up to what, 45 minutes, an hour? Spitballing it at one lie every two minutes, which may well be low, that’s around 25 factual lies a day.
He was also doing his shit even back in high-school when he tried to make every failure look like a success, and when he was still working closely for his dad in the 70s some newspapers even mocked him for promising the moon but delivering a moonpie. They noted his tendency to exaggerate everything he did as the best and biggest even when it plain to see that it was not.