One of Obama's favorite phrases was "the wrong side of history". Essentially, anyone who who didn't espouse progressive beliefs was labeled by Obama or the left as on the wrong side of history. It's that kind of stuff that helped ripen the fields for Trump.
While there have always been people willing to follow a demagouge like Trump, 8 years of normal, hardworking Americans being patronized by the left drove people to support Trump who would ordinarily find him repugnant. All he had to do was tell them they're right and shouldn't feel bad about believing the way they do.