I doubt if the reason for them developing the currency is to affect Bitcoin because I'm not seeing any correlation between the two. This is a currency we are talking about that will be used as legal tender in the countries and is not like they don't have any existing currency before and this doesn't affect it.
I also don't think it has anything to do with influencing the price of Bitcoin or reducing its popularity. There is a global trend to gradually get rid of the hegemony of the dollar, which can start from reducing its use in global trade exchanges. In parallel with the BRICS plans, I read yesterday that the United Arab Emirates agreed with India to complete trade exchange deals between them in rupees, which can be considered an additional step in the same direction, although this is outside the BRICS framework.