Yes they do own the rare earth deposits for electronics but they will have to hold them for a long time if there is a collapse. No buyers for the electronics. U. S. , Europe and maybe Japan all collapse I see China going back to hard core communism but many there will die and there will not be many buyers for there products.
China has always been afraid of a cheap dollar which would make all U. S. products very cheap to buy. This happens why would South Americans, Europeans, Central Americans, Canada, Europe and many other countries buy from China when they can buy the same products made in the U. S. for cheaper?