"Not sure why they would do this though."
Trump has recently threatened to tariff the crap outta the BRICS if they attempt to put forward a new currency to flog against the dollar. He's also been calling China a 'threat actor' and pushing all sorts of tech restrictions against it.
Brics need a currency, and China is showing the depth of it's pockets, is my guess. The Yuan isn't a new currency, and the US can only tariff China so hard without cutting it's own throat, which I believe is why he threatened Canada and Mexico with 25% tariffs but China only 10%, which, correct me if I'm wrong, is actually being imposed - at least I've heard no action against fentanyl production or provision of precursors by China - while the tariffs on Canada and Mexico were able to be dropped.
If China can drum up commerce using it's Yuan across the BRICS, it can turn that tariff into a much more powerful position in the BRICS, despite Russia's apparent turning to redemption in the US market. Perhaps even more if Russia's sanctions in the West are dropped by the US and China can stop turning away their tagged tankers and bank xfers. I won't pretend to be able to reckon whether that can make up for a 10% hit on exports to the US, but I suspect it could, particularly if it doesn't have to dodge sanctions on Russia anymore.
Thanks!