Don't think that the Koreans are that stupid. They must have carefully analyzed both Bitcoin and Bitcoin Cash. And a major part of the investment came from institutional players, as per the ground reports. These people might have found something positive about the future prospects of Bitcoin Cash. That said, even now there is hardly any chance of BCH overtaking BTC.
Maybe they figured out that Bitmain is backing BCH, and controls a majority of Bitcoin hash power!
It's very interesting that BCH and BTC seemed to be perfectly inversely correlated for the past 2-3 days. I know it's possible to manipulate these illiquid markets, but maybe that's not it. Maybe there really is something to this Metcalfe's Law stuff, and maybe we are seeing a network split occur in slow motion?