It was their mistake to build up a huge stack of essentially worthless currency ....
I think you are mistaken, my friend. China build a whole industry in four decades while the West destroyed its industrial base by unsound monetary policies. We have sold the rope that China will use to hang us, as a figure of speech.
I completely agree with this side of the equation. But it was a mistake to build up that stack of fiat of that size, and it seems like the Chinese government agrees and tries to correct it. Otherwise they would not buy gold in such quantities that their holding will soon surpass that of the US (assuming it is still there). Otherwise they would not buy 5% of Ukraine.
Bitcoin is a tiny part of the equation, but it fits in the general pattern.