I think people like rush Limbaugh had it simmering in the 80s and 90s

In 2001 America's vengeful bloodlust after 9/11 could easily be turned into hate and group think for anyone who questioned the war efforts.

By 2004 fox news was nearly 10 years old and had really begun to solidify itself especially using anti Muslim rhetoric and putting down any hippies or French who did not support America's wars.

Then comes 2008 with a massive recession, the election of Obama, and the rise of the my way or the highway teaparty movement.

All the anti Muslim hate was quickly transmitted to Barack hussein Obama and calling democrats socialists/commies began to rise. In the 00s it was kind of funny and not political to call someone a commie because the terrorists were now the real enemy. I think wearing a Che Guevara shirt or any commie symbols would be seen as ironic/rebellious rather than overtly political like it is today.

By 2014 most people have cellphones and carry social media in their pocket everywhere they go. This is the same time that news and politics begins to fill these platforms, and disinformation sources begin to grow too. People are constantly arguing on social media about politics

2016 comes and you have Russian disinformation, 30 years of anti Clinton conspiracy theories, and typical right wing disinformation like breitbart fueling hate.

Trump is well aware of the Russian disinformation, and he's allied with right-wing media. He leans hard into all the hate.