Because the corruption and waste is spread among competing crooks with differing and competing interests. They act as a check on one another.
No one set of crooks can manipulate the currency in BRICS. It’s a basket of crooks.
But they’re all objectively worse crooks that manipulate their currency more. So how does that produce a ‘win’ over the West?
Combining weak currencies just has them racing to beggar each other.
I’ll happily outline the faults with the US dollar and the crooks that manage it, but it remains the ‘cleanest dirty shirt’ in the world of fiat laundry. People looking to South Africa, etc. for some kind of global economic savior strike me as delusional.