it's mostly due to the unfortunate effect of the boy who cried wolf
ppl have come to expect politicians to not do the grandiose stuff they promise to do, but now the day's finally come
That actually makes sense. Hillary promises to behave like a competent, rational leader, and people assume she'll actually be corrupt. While on the other hand, Donald Annoying Orange promises to do a whole lot of crazy stuff, and people assume he'll actually be a competent leader.
Going off of this logic, if Humble Water Filter Merchant ran for president, he would be the most competent person ever elected.