The wearing of masks along with other measures by the general public undoubtedly contributed greatly to lessen the burden on the government to do tracing and testing.
As of yesterday, 250 have died from the coronavirus in Korea. By tonight or certainly tomorrow night, according to worldofmeters.info, the US will top 70,000 deaths. Same data source for both Korean numbers and US numbers.
It's just like Forrest said, "stupid is as stupid does".
Since underlying conditions have an impact on death rates, I just did a quick search and found out 36.5% of US adults are obese, while only 4% of South Korean adults are obese. Coincidence?