I suspect that a lot of his appeal is that despite inheriting his wealth, he behaves like someone who's grown up without it and suddenly won more than he knows what to do with.
I think he appeals to that subsection of society who relate to his simplistic ideas, greed, arrogance, distrust of others and craving for power and recognition. They found him relatable and maybe even saw themselves in him and believed, despite it being counterintuitive to the attitudes of his they supported, that he had their best interests at heart.