> Something happened in the last twenty years or so that increased our polarization.

I'd expand the timeframe to 30 years and say the biggest contributors to this are the rise of neoliberal politics combined with globalization leaving a lot of working class people "behind" while corporations made ever more and more profits, combined with the rise of the Internet where the most outrageous content gets the most clicks/likes/eyeball-time with next to no institutions to provide as "quality filter".

Stuff like antivaxxers, flat earthers, "great exchange of the white people" and other conspiracy bollocks was relegated to physical mailings of fringe groups naturally limiting its distribution, nowadays the reach capability is in the millions for everyone.

In addition, countless fuck-ups (aided by propaganda) demolished trust into journalism and experts in general, which led to the erosion of fact-based viewpoints as the base for democratic discourse.

The end of the Cold War should not be dismissed. The West had a common-enemy. This served to unify things somewhat.

Looking back, it's easy to fit these large changes -- like the internet and globalization -- to any current outcome.

> great exchange of the white people

What is this referring to?

AKAIK It refers to demographic trends in the Western world where white ppl have lower fertility rates than other groups.

The actual term is "great replacement", and it's a conspiracy theory regarding an alleged systematic replacement of native Europeans (i.e. "whites"). The Christchurch shooter was a big fan, apparently.

It's a way to relabel normal immigration by upstanding people into nefarious "white genocide".

I agree with you, but you should have expressed this in a way that didn't assume bad faith.

> Something happened in the last twenty years or so that increased our polarization.

This has happened all over the world. The obvious major thing that's changed is this thing right here: The internet.

Social media has replaced "mainstream media" as the source of our news and our opinions. And so we have a new opinion landscape.

I think it's something else (or perhaps I'm only elaborating on your point)--the proliferation of postmodern ideologies (e.g., progressivism) throughout our epistemological institutions (principally the media and the academy) which explicitly cast doubt on objectivity and put "lived experiences" (as though there is another kind) on par with empirical research. Progressivism often goes so far as to condemn objectivity (including math, physics, biology, etc) as "white supremacist", "racist", "patriarchal", or otherwise "problematic" (this is literally the textbook position on objectivity). This along with the secularization of America largely errodes our trust in the institutions which used to give us a common source of truth.

This gives license to all sorts of denialism and conspiracy theories--the right denies climate change, the left denies biological gender differences, and both sides have their anti-vaxxers and flat-earth theorists. Without common "truths" to counter our tribalist tendencies, we are being pulled toward extremes.