Hanson's Razor - Never attribute to stupidity that which can be adequately explained by (unconscious) malice or selfishness.
There, I said it.
I don't think that votes were messed with, I don't think that any (horribly insecure) voting machines were tampered with, and while jerrymandering is totally a thing I don't think it had anything to do with the election. I think that appealing to people's most deeply held beliefs, the ones that few are willing to talk about openly had everything to do with it.
Donald Trump is everything that USians want to be, deep down inside. Let's be honest: Whether or not Donald Trump is really as rich as he says doesn't matter. What matters is that many people believe he is rich. In the United States cultural mindscape that equates to power. As he's bragged about on television repeatedly, he's done some pretty heinous and ignorant things and gotten away with all of them. That show of power demonstrates that he's effectively above the law. He's on television a lot, which to the USian cultural mindset equates to fame. Fame is a form of power all its own, because to be on television you have to have access to the media somehow, and having access to the media means that he can reach everyone watching a television, listening to a radio, and haunting every social network without even trying. If you follow his Twitter feed you can observe his antics first-hand.
USians love money. USians love power. USians love getting away with things. USians love fame. He's everything every USian wants to be - he's the American dream.
And who doesn't want to be like him? Who doesn't want to be Bruce Wayne, who's stupidly rich, gets away with the craziest shit during the day, and still has time to himself to practice being a badass after dark? Who doesn't want to be Tony Stark ("Genius, billionaire, playboy, philantropist."), hook up with Playboy centerfolds, and kick asses around the world while getting away with it (mostly)? Who doesn't dream of being Lex Luthor, an amazingly wealthy industrialist who just happens to want to kill Superman, the all-American do-gooder?
Donald Trump is all of those fictional characters brought to life (modulo being a hero, though I'll get to that in a second), every badass example of the American Dream that people think they have. Throughout the entire election he showed off all of those qualities writ so large you could see them from orbit, and people ate it up. The hero bit I mentioned? He promised a nebulous effort to "make America great again," which just about everybody who's worried about their lot in life ate up and went back for seconds. Afraid that the middle class is vanishing like spilled water in the desert? Hate "them other folks" but either won't admit it out loud or don't even realize you're racist? Openly racist and hold demonstrations calling for ethnic cleansing in the United States? Want reassurance that anything sketchy you might be up to might get a pass because Trump's promised to make it go away? Just want to watch it all burn? Trump not only validated those feelings but openly embraced them among his constituency and campaign staff. He promised to make the boogiemen under the bed go away. Everybody on the fringe, from the folks who took somebody's attempt at trolling seriously to genuinely scary people sat up and howled when the dog whistle blew.
You don't have to rig an election when you work to be the person that everybody identifies with. When the people of the United States voted for Donald Trump, they actually voted for the kind of people they themselves most want to be.
The bed's made, and bedtime's near. Nightmares are coming.