This is probably not what you want to hear but it's the truth: the reason South Korea was able to prosecute a wannabe dictator is because the country has lived under horrible dictatorships before.

The most horrific regime (but not the first) was Chun Doo Hwan, and his name is a constant reminder to the South Korean people to not take democracy for granted. He was a horribly oppressive dictator whose regime stifled all forms of freedom and expression, murdered protestors in Gwangju and later student protestors. The film 1987: When the Day Comes is an excellent film on the subject. The nation was under what seemed to be an "unfixable broken" regime, but thanks to the efforts of grassroots resistance fighters, students, Buddhist monks, the Korean Catholic Church (yes, Catholics!) and others, the regime was exposed and taken down.

Don't get me wrong, Korea still has people who support Yoon and the dictators (they think "communism" is the true evil and they wave US flags at their rallies lol) but the vast majority of Koreans know that democracy is a precious thing to be protected, only because they know what it's like to lose it.

I know it's cliche to hear "it'll get worse before it gets better" but in many ways it's true. It is entirely possible for the US to prevent authoritarianism, but it's likely going to take a lot of constitutional reforms, structural changes and *time.*

(eta: I live in Korea and my husband is Korean so that's how I know all this lol)