- The 2016 elections were a choice between two evils, and people couldn't see any third way ─ or perhaps they didn't even want to contemplate a third way. Some US states don't even allow for third-party candidates to run for president or even to be voted on.
- There are people who were feeling left out in the cold by the political establishment of the day, and given that Trump came from outside of that establishment, people thought he'd be a change for the better.
Either way, it was through the existing voting system that Trump got into the White House. There was no military coup involved, nor any supernatural or extraterrestrial intervention.
Of course, there was a certain degree of dishonesty involved, such as what Cambridge Analytica did with the information they got off of Facebook, and the extent to which Facebook allowed them to get away with it. And there may or may not have been Russian intervention ─ it is difficult to say, and even more difficult to pin it down on Vladimir Putin himself.
But all things considered, while the dishonest tactics may have helped Trump in his electoral victory, I still think he would have won without it, and he's still enjoying the support from a large part of the US population. There are still people wearing MAGA hats. So that's what you have to start looking at. Why are those people supporting Trump? Why do they believe in him, in spite of the fact that he's a deranged buffoon, a narcissist, a nepotist and a Mussolini-wannabe?
By the same token, why did so many people support Hillary Clinton, even though she's a megalomaniac who lies just as much as El Donaldo the Banana Republican™? Why didn't those people see Hillary for what she really is? After telling the corporate moguls that what she says in public isn't how she really feels or what she really plans to do? And after the way she destroyed Bernie Sanders' chances at running for Democratic nominee?
Start there, and you'll get a lot closer to that second floor already.