How this all came to be
Looking back, there's no doubt in my mind. 9/11, Amerithrax etc. caused a huge traumatic injury to the fragile psyches of a majority of the American majority.
The resulting wave of "patriotism" was actually a counteroffensive in the decades long culture wars- just daring any of the outsiders to say anything bad about Our Troops or 'Merica. "The left" insofar as anything of the sort actually still existed, fell in line as well.
Following the failed military adventures andGFC catastrophe, The Tribe regrouped under the banner of the Tea Party (organized by RW provacateurs like Dick Armey) and then after 8 years of frustration over the foreign guy surviving, they were primed for Dennison.
Re: How this all came to be
The Reagan reboot of nationalistic patriotism was always a fragile thing.
It served the purpose in holding things together a bit longer while The Grand Bluff ended the Cold War.
But you never want to forget that you were bluffing.