It's not limited to BRICs but many emerging economies or distressed countries PRC wants to gain influence. Dollars attached to specific PRC projects, i.e. BRI, so they buy PRC industrial inputs, goods, equipment, contracts PRC SEOs to build XYZ. It goes from a Chinese bank to a Chinese contractor who buys other shit. But the shit they are not buying is US treasuries, and even if they did, not at PBoC/central bank for storage low yield rates that subsidizes US debt. Sometimes there's more generalized debt servicing swaplines, but regardless When dollars come due, PRC can take rmb/commodities/assets (rarely aka debt trap). If borrowing countries payback in USD, then cycle repeats. PRC is basically exploiting UDS network / liquidity effects without paying exorbitant privilege. Well they do pay, as in they take on lending risks, but their USD reserve is inherently not safe anymore post RU sanctions, so might as well as use it now.