It’s all part of the protection racket. The Saudi monarchy writes their oil contracts with other countries in US dollars so that the other countries have to buy up lots of dollars in order to fulfill their contracts, and the US in turn looks after the security of the Saudi monarchy.
If the Saudis should start writing some of their contracts in Chinese currency or Euros, this would have a big influence on US influence on financial markets throughout the world.
We have a bingo. Protection is the word of the day...
They would also be in violation of their treaty with the U.S. to trade oil is U.S. Dollars.
Hence the name, the Petro dollar.
Chinese currency is worthless and the Euro is volatile. Zero chance they ever dump the dollar.