Besides, Bitmain seems to have some impact in the economic and maybe political level which may explain this flux situation
Yes. It's all about connections. It has been the same with various exchanges during the major shutdown. Guess what exchanges got a very soft treatment.... Right, Huobi and OKCoin. These exchanges were literally beaten up and couldn't walk anymore, and suddenly they pop up and rule the crypto market again with their volumes. It has nothing to do with how much of a great exchange they are, but only because of their connections. Not sure what percentage of their volumes are fake, but it's no longer coincidence that these exchanges always hold top positions in this market....