Putin would step right in to fill the same exact role

Russia unlike the US doesn’t have the corpse of the British Empire and 50% of the world’s industrial capacity to piggyback off like the US did after WW2

Empires do not all have the same capacity, means, or internal structures that can guarantee a one-to-one replacement theory like you just asserted

The idea that the Ruble could ever become the equivalent of the US petrodollar is anti-historical and anti-materialist and if that won’t happen how on earth would Russia dominate global capitalism the way the US currently does?