I lived in South Korea 2019-2021. On top of what you said above, they have a very good very intense contact tracing system, in SK the phone/bank/government are pretty inter-connected, it's not difficult for the government to literally hunt down cluster infections and force people into quarantine, and they did. They sent out over sms the exact times and locations of places people who had covid visited, etc, etc. I think contact tracing, Koreans taking it very seriously, wearing masks correctly, actually social distancing kept things under control. Koreans a very good at following instructions when they decide to, and they do it diligently.

I'm not sure how I am expected to answer that question without knowing which country you are asking me to compare.

Switzerland has a higher life expectancy than South Korea, and has a very wealthy and healthy population.

Spain and Italy have both held the titles of "healthiest country in the world" in recent years.

All three have incidence rates more than an order of magnitude larger than South Korea.

Wearing respiratory protection equipment protects against respiratory contaminants. Testing people and tracing contacts helps to contain outbreaks. The answer is really that simple. South Korea was one of (if not) the first countries to start an aggressive testing and tracing program.

On TV, I watched their citizens line up in cars at mass testing sites months before my multi-billion-dollar healthcare conglomerate here in the US even had testing available at all.

That was only the first time, and only after the virus was everywhere. SK reacted much more rapidly when it initially came to them.

Furthermore, Schengen. SK are for all intents and purposes an island, and everything and everyone must come by either boat or plane, which helps with control.