I was also very surprised to see it drop to 0% in that chart too, especially considering I saw an article a few days ago that China vowed to hunt down and stop all bitcoin miners in their country within a year, but I didn't see any other data to suggest otherwise.

So yeah, I believe that article that there could still be 20% of mining hiding somewhere within China and using VPNs.

But it definitely resulted in a big shift away from China, regardless.