Note: This has nothing to do with policy. I am not defending any political party or candidate, but I am offering a reasonable explanation. I don't care to hear about your political persuasion.
We can look back to Ancient Greece for clues that Trump's victory was all but inevitable. In the days of Plato and Aristotle, a group of scholars called the Sophists opened private schools where they promised to teach people to be effective, persuasive communicators. They were masters of the art of Rhetoric, and taught that a speaker who used emotion, logic, and credibility would be very effective.
Looking at the election, Trump had a clear advantage over Hillary on emotion. His events were boisterous and the crowds were excited.
Hillary, with her experience, should have won on logic, but she got away from that and tried to focus on criticizing Trump. In doing so, she turned away from her strength in logic, while Trump focused on policy down the stretch. Another advantage for Trump.
Credibility was the most interesting. No one will deny that Trump has said crass, inappropriate things for years. However, the Democrats, in once arguing that "character didn't matter" in support of Bill Clinton and his actions, could not really argue too forcibly against Trump's words. Trump's campaign never let up on on Hilary's email scandal, and the criticism started to stick. Most polls showed that the clear majority of American believed that she was dishonest. So, this amounts to another advantage for Trump.
This gives Trump an advantage on emotion, logic, and credibility. Add to this the effectiveness of his slogan, which we all know, and it really should not be a surprise that Trump won.
In Ancient Greece, the Sophists were not always popular, but they did not care. They claimed, and proved, that they could take any side in any argument and win. They also said that they could convince any audience of the truth as they defined it.
Now, which candidate from the election does this sound like?