Look at what America did to their ally South Africa, the ambassador accused us without proof and our currency dropped like a rock. The US also had its army in Syria protect private military contractors who protect US companies extracting oil from Syria. They're hypocrites as China is their biggest trading partner. France produces 70% of its electricity from nuclear and gets the majority of its fuel from Africa. And West Africa is just as poor as it left them.
India and China having border skirmishes don't make them sworn enemies of each other. In fact, China is one of India's largest trading partners. The US and Canada even has border disputes; see https://en.wikipedia.org/wiki/Dixon_Entrance.
Also, it's not a military bloc. And you can understand why the Global South countries would want this alliance to grow their economies and be less reliant on Western imposition. On average, African countries loans cost 4% more than America and 8% more than Europe, they're being taken advantage of and their natural resources depleted.
And now those countries want to come together to build up their economies through the New Development Bank which aims to increase local currency borrowing to 30%.
The BRICS countries constitute more than 50% of the population and 26% of the world's nominal GDP but have only 14% of the IMF's voting rights.
They aren't looking to unsettle the dollar, but be less reliant on it.