Two reasons really.

1) there is a lot of new money in China. Hundreds of millions lifted out of poverty, more millionaires than in the USA. Tight capital controls mean it is difficult to diversify and move your money out of the country. Bitcoin helps with this. Unlike Korea, it is not your average middle class who is holding bitcoin, it is the richer folk.

2) cheap electricity from hydropower. They have more electricity than they can use themselves.