[jdsteel]

When you are having financial difficulties, as these countries are, you sell what you can to get needed cash. US T notes and bonds are easily traded and if they sell them before an interest rate increase they may get a bit more than they would after the increase. Just makes sense.

[Alberta's Child]

I would have thought that China would have a huge incentive to hold dollar-denominated assets even if they don't provide a great return on investment as measured in U.S. dollars.

If you hold a U.S. Treasury bill paying 2% interest, you're not in good shape over the long run. But if you hold a U.S. Treasury bill paying 2% interest and you are a country like China that devalues its currency by 20%, then your return on your initial investment looks more attractive.

[Enlightened1]

What about the BRICS Central Bank?

I think that is the main reason.