Someone was telling me years ago that Putin/Russia held the dollar by the throat and could destroy its value if they stopped using it and switched to the Euro instead.
My undertanding is that part of the value of the dollar is that everyone agrees totally with what it's worth. Therefore, it is a safe currency to trade in, even for those countries with their own currency. It remains stable and so does not fluctuate in value too much. So part of it's value is that everyone sees it as a global currency, so it's always worth having dollars because dollars are a safe bet.
So Russia trades in US dollars. All it's resources are priced in dollars. This benefits them but also benefit the US dollar because Russia is a massive trading entitity so lends weight to the 'global currency' viewpoint.
IF Russia chooses to not trade in US dollars, it may convince key trading partners not to also. So, when a number of countries no longer use US dollars are their stable currency, it gets less stable and less global as a result. And looses value because of it.
I suppose it's not so clear cut in that the US could choose ot to allow Russia to trade in US dollars, if the EU do the same with Euros, what stable currency can Russia trade in? Yen? Yuan? Does that hurt them to do so? I'm not sure...