I guess that is something that was not predicted but still happened.
For many years, the white, middle class, semi educated demographic... (you know who I mean; the ones that worked in the steel mills and the factories and the mines, and who farmed the land and provided soldiers for all of America's wars, in other words, those who were once the backbone of America) have felt left behind, taken for granted and disenfranchised.
Now, whether or not any of that is actually true is arguable, and in any case, largely irrelevant. Its what this demographic
perceives as being true that is important. This year, for the first time since records were kept,
white births were outnumbered by non-white births. By 2044, whites will be a minority in what that demographic considers to be its own country.
IMO, it is the perception of this demographic that they have been largely forgotten about that has led to many of them who might never have voted before to vote for Trump. In Hillary Clinton, they saw an establishment candidate who they perceived as representing
"more of the same old same old" ; in Trump, they saw someone who was offering something different, who said the things they wanted to hear.
I while I consider Trump to be an intellectual doofus, he is also a cunning strategist (don't ever make the mistake of confusing cunning with intelligence). He knew the fight was going to be a close one, he knew that a single demographic could be the difference between winning and losing, he figured out which demographic was most likely to be the key, and he targeted it with a vengeance.