Yeah, I could triple the "read this to learn more" links and it'd still not cover all of it.
"The entire history of the Republican Party since Goldwater, our bad system of elections, the entire history of postwar 'think tanks', the McLuhan-sense 'message' of TV and especially the Internet, and a slow-motion more-successful knock-off of the Business Plot" covers a lot of ground.
Long story.
https://en.wikipedia.org/wiki/United_States_antitrust_law#Ri...
https://en.wikipedia.org/wiki/Dark_Enlightenment
https://en.wikipedia.org/wiki/Roger_Ailes
https://en.wikipedia.org/wiki/The_Heritage_Foundation
https://en.wikipedia.org/wiki/Moral_Majority
https://en.wikipedia.org/wiki/Federalist_Society
https://en.wikipedia.org/wiki/Bush_tax_cuts
https://en.wikipedia.org/wiki/Tax_Cuts_and_Jobs_Act
https://en.wikipedia.org/wiki/Citizens_United_v._FEC
https://en.wikipedia.org/wiki/Neoliberalism#United_States
https://en.wikipedia.org/wiki/War_on_terror#Costs
That's a start.
And a rise to dominance of populist conspiratorial thinking. ContraPoints had a good intro video about it recently.