A lot of the boards are likely still designed in the west, but manufacturing to the required scale can be a dirty business. It moved east because there was a large population who would accept wages a lot lower than western counterparts. Health and safety standards are expensive maintain, if you move to countries with lower or non-existent controls then it can be much cheaper. When you can chuck toxic wasted into a river and make it someone else's problem, it's hard for developed countries to compete.
There is only Bitmain left. All the others have been defeated. The know-how has followed the manufacturing capabilities. Moreover the culture isn't under attack, safety is provided at all level and harmonious society can prosper in China...
