How Extreme Bipartisanism Rose in the United States

Reagan kills the Fairness Doctrine (1987) - Broadcasting used to require stations to present both sides of controversial issues. Reagan's FCC scraps it, which opens the door for openly one-sided political media.

Rush Limbaugh fills the vacuum (late 80s/early 90s) - Without the Fairness Doctrine, AM radio becomes a playground for right-wing talk radio. Limbaugh pioneers the format: rage, tribalism, "us vs. them." He builds a massive audience that learns to distrust mainstream media entirely and treat politics like a team sport. Copycats flood in. The Dems try to respond with 'Air America' but it never gains any traction and would go bankrupt by 2010.

Clinton passes the Telecommunications Act (1996) - This deregulates media ownership, allowing massive consolidation. A handful of corporations buy up thousands of local radio and TV stations. Local journalism dies, replaced by nationally syndicated content - mostly conservative talk radio. Meanwhile Clinton's "New Democrat" strategy abandons the working class in favor of corporate centrism (NAFTA, welfare reform, crime bill), leaving millions of people economically gutted with no party speaking to them.

Fox News launches (1996) - Roger Ailes builds an entire cable network around the Rush model. Now the echo chamber has a 24/7 television arm.

The snowball effect - By the 2000s you have a massive chunk of the country that has spent 15 years marinating in media specifically designed to radicalize them, distrust institutions, and view Democrats as existential enemies rather than political opponents. The GOP realizes they don't need to moderate - they just need to feed the machine.

Trump is the inevitable product, not the cause. He didn't create the base, he just spoke their language better than any politician before him because he literally learned it from watching Fox News all day.

TL;DR: So the short answer to "how did we get here" is: deregulation of media created the conditions for a right-wing echo chamber (which later would be the basis of MAGA,) Democrats abandoned the working class which encouraged them to look for help elsewhere, and nobody in power had any incentive to stop the radicalization because both sides were benefiting from it in different ways.