Honestly I see a "rock and roll" sign on that chart. 

Anyway South Koreans does really have high interest to cryptocurrencies. An exchange won't operate there if there's no interest and volume at all. And this ain't new as far as I remember there are also hack incidents that included that South Korean-based exchange (bithumb).

Addition:
To know more about the volume of different countries: https://coin.dance/volume/localbitcoins