This is what I think happened (in part - there were many other contributory factors, of course).
I know these rural whites who swarmed up and elected him. I live with them. This is the narrative:
"This was a great country, the best! Hell, we saved the rest of the world’s bacon in two world wars! My granddaddy only had an 8th grade education, but he had a good job in the plant, and put food on his family’s table. My daddy dropped out of high school, but he had a good job at the plant and took care of us and kept us all in line.
"But then They closed the plant down, and sent our jobs to a lot of furriners. And then They let all the damn furriners in to take our jobs. And them furriners hate us, and want to kill us all. And now They wanna send even MORE of our jobs overseas, looks like to China or Japan. Hell, I thought we beat them fuckers in the war!
"All we wanted was for Them to open up a couple plants nearby so we could have a job and take care of our own. That’s all it woulda took. But the Democrats had to get all fancy-schmancy bout them gays and minorities, and told us we was stupid and hateful but didn’t tell us why. The Republicans was a little better, ‘cause at least they was Godly and didn’t hold with baby-killin’ and perverts. But when you get right down to it, all any of 'em really wanted to do was to line their own pockets, and raise my taxes and give it away to __________ who didn’t do a lick a work to get it.
"But Trump, now! There’s a man! He’s Godly - oh, he might cuss a little, and raise cain, but judge not lest ye be judged! He don’t need nobody’s money - he’s got his own. And he ain’t afraid to stand up and tell it like it is! This guv’ment ain’t done a damn thing for anybody, but he’s gonna set 'em all straight and get some work done! They call him all kinda names, but They do that to us, too.
“So screw the gov’ment! Donald Trump is wild, and free, and white…
…just like me.”
(Sorry; I literally do not know what I am typing, nor why I am typing it. I have long felt sorrow and pity at the plight of these people, whose tidy lives are being torn apart by global socio-political-economic-technological forces far beyond their ability to comprehend…but still…damn it all.)