The reason China's economy has been growing so much is not because they've been mining bitcoins. It's because they have an enormous, impoverished, and largely agrarian population that has been able to reap huge productivity gains from relatively inexpensive investments in productive capital. If your broke ass citizens are working with hand tools and then you buy them power tools, their productivity will increase quite a lot. Compare this to the west where our workers already have power tools and capital investment means buying better power tools will increase their productivity just a little bit.