There's plenty of engineering shops over there capable of doing the chip design, and at a cut rate, AND as a contract gig. Also most of the chip foundries are in that part of the world these days.
Stateside and in Europe where most of the other major tech infrastructure is (foundries and the engineers to make them) the systems are locked into industry/company demand. Intel/AMD/Nvidia/Motorola/Etc... have large engineering teams capable of designing them but they're too busy making the general use devices those companies are in the business of then producing at THEIR foundries.
So basically China and eastern Asia are the only areas in the world with an existing knowledge base and the capacity to produce the chips.
Then you can add on the fact they're lower cost to produce there, AND that a large segment of the mining community is IN China you have a pretty clear picture. The nation's low cost of electricity only adds to the incentive to develop and deploy them.
AMD and IBM no longer have their own founderies - they shed them as a "cost saving measure" some years back, forming GlobalFoundries in the process.
Nvidia has never had their own foundry - they do seem to have some long-term contract with TSMC and recently started using Samsung for their 1050 and 1050ti cards.
I'm not sure if Motorola ever had a foundry - if they did, it was a LONG time ago and long since split off or sold off.
Some or all of the major MEMORY makers have their own foundries though, Micron (and Samsung of course) come immediately to mind, and I'm pretty sure Hynix as well.
China cost of electric - varies. There are some parts where big hydro projects went in that have huge oversupplies and VERY cheap power, there are other parts that don't have a good power grid at all and the cost is a lot higher.
They seem to be working on getting more industry developed in the cheap power areas, and at least somewhat on power transmission, but they're quite a bit behind the US in HV transmission line construction experience (we've been doing that for fairly close to a CENTURY now, in part due to the Hoover and Grand Coulee dams both of which don't happen to be close to ANY major cities).
