This used to be the case long before the CCP banned Bitcoin mining in China, you were able to see a direct correlation between BTC price and mining hashrate/difficulty as well as gear prices sometimes, but in the past couple of years since the U.S became the largest mining hub in the world, everything changed, there is nothing 'rational' happening anymore, it has to do with many things that are vastly different in the U.S, Tax laws as phill mentioned, the type of money used (investors money which is a somehow different mindset in China), and many other variables that makes mining unpredictable.