> Because those people saw him as lesser evil compared to Clinton? If there was another not-Clinton candidate, they'd have voted for him/her.
As a Trump voter - but not a Republican - this pretty much sums it up. His SCOTUS list and the formation of his "Second Amendment Coalition" nudged me from the "he's better than Clinton" to the "maybe he'll deliver something I want" column, but there are no circumstances where I would have voted Clinton.
> It'd be interesting to see Sanders vs Trump in parallel universe.
I think it would have been a slaughter in that case, instead of the squeaker it was. Trump's biggest challenge was winning over the libertarian wing of the GOP. If he were against Sanders, that part of the party would have been locked down from day one.
I think it is generally underappreciated how bad of a candidate Clinton was. Many people for good reason were frustrated by the status quo of politics and the Democrats would probably have had a hard time to find someone playing more into this. Her entire platform seemed to be to continue what already was happening except that she will be there first female president; she was heavily associated with a previous president; the way she and the Democratic party treated Sanders played badly into her being the heartless, corrupt establishment. I don't think I met anyone who really was excited to vote for Clinton her entire virtue was not being Trump. I'm honestly certain that pretty much anyone could have beaten Trump except Clinton.
It also shows to me how broken the US election system is. We badly need something like approval voting. It's unacceptable that we ended up was two candidates who both had awful approval ratings.
What I gathered from Trump voters was that they looked for someone to shake up a system they viewed as not working. So Trump was that guy. It was pretty clear that voting for Clinton would prolong the status quo. It's unfortunate that the American system doesn't provide choice.
Of course I do not have inside information, but if I had to guess...
Trump basically stumbled on this untapped political bounty more or less by chance, but he has smart enough to recognize its value and design a political persona that would speak directly and effectively to that group[1] The fact that there was otherwise no obvious leader around whom the Republican party could gather gave us Trump-the-candidate.
Trump-the-president was a slightly more complex matter. There was another candidate that was able and willing to tap into this new constitutency of the politically ignored: Bernie Sanders. Unlike the Republicans, there was also one obvious Democratic leader around whom the preexisting constitutencies of that party could gather. The problem with Hillary Clinton is that she is the very incarnation of political status quo; instead of picking Bernie as her vicepresident she doubled down on keep ignoring the chronically ignored. She went as far as to antagonize them, mistaking the whole of the group for a very vocal minority of them, - the racist misogynist know-nothings.
I do not need to tell you that was a huge mistake. The way the American politics work, you win by winning most battles, not by winning the biggest battles. Even if the majority of individual votes went to her, she still lost; and she lost because she decided to abandon a number of critical camps. Or rather, because by failing to notice this new political constitutency, she lost electoral votes that historically should have been Republican. She did not notice the balance of power shifting under her feet. Again, having Bernie on her team would have helped her to put a fight in most of the battlefields that Trump winned just by being the only one to show up there.
[1] I am using the term "group" loosely here. The way I see it, it is more a coallision of different disempowered groups that had little in common beyond feeling cheated by the status quo. By example, I've heard a number of women that voted for Trump were mothers and wives of the millitary, who saw Clinton's warmongering as an existential threat to their families and voted accordingly. Trump's friendly overtures towards Putin make much more sense if you frame them as subtle signaling to that particular subgroup.
It'd be interesting to see Sanders vs Trump in parallel universe.