Howard Zinn wrote a book called "The People's History of the United States". One of his themes is that the upper class has always let enough money flow into the hands of the middle class that the middle class will identify with the upper class rather than the working class.
I think what has happened in the last 30 years under Democratic and Republican presidents alike is that the upper class has abandoned that strategy, become more avaricious, decided to go for all the gold, and damn the consequences.
We are becoming the world's richest third-world country. More and more of the country's wealth is in the hands of a small few who are working to make sure they keep it. The Republicans may finally achieve their dream of abolishing the inheritance tax. Collapsing infrastructure. Few social services. Disdain by those at the top towards everyone else. A ruling elite. Perversion of democratic institutions. Trump's agenda simply is more upfront about it.