Moving to a new country isn't as easy as it sounds. These people have a life in China, family, children, friends. All that can't be abandoned over night just like that. Not to mention familiarizing yourself with the regulations of the new country, finding an appropriate and cheap location to set up your farm, and physically moving your equipment from point A to point B. All that takes time and money. There is also the language barrier, cultural differences to consider, etc. Of course it's doable when someone forces you into it, but I believe that's not what the Chinese miners want to do.