The Shanghai oil futures market is a challenge to the dominant role of the US dollar in the oil market.
Saudi Arabia is a key player and now has good relations with Russia.
The US has imposed sanctions on Iran, Russia and Venezuela.
Weaponization of the US dollar by the Obama and Trump administrations has led to accelerated dedollarization. Freezing accounts in dollars and blocking dollar transactions are economic weapons.
China and Russia have developed payment systems that allow them to dispense having to employ US dollars
https://seekingalpha.com/article/4223468-decline-fall-petrodollar