I feel everything goes around and around in cycles.
Before 9/11, and after Watergate (except for the "Reagan Revolution," Americans were usually pretty apathetic about their politics---except for those particularly interested in politics. I was pretty apathetic.
There wasn't as much of a reactionary backlash as I expected following 9/11. I expected more draconian measures from the Bush government, frankly. I think the restraint shown, for the most part, was admirable.
What really set the present political storm going, I believe, was the Great Recession, starting in 2008. People were losing jobs left and right, and not getting them back left and right. Being unemployed often reactivates dormant political feelings. The blame was laid squarely upon the banking industry, and the government "bailing out" the banks. This got people angry with government, whom they felt ignored their concerns. This reactivated many other grievances...like immigration and "political correctness." This started the ball rolling towards Trump.