The origin of the petrodollar was a 1974 agreement between the US and Saudi, that Saudi would only accept dollars in payment for their oil. Other oil exporters went along. This meant that foreign countries needed to buy dollars to pay for oil imports. This strengthened the dollar’s place in the world economy, with great benefit to the U.S.
Interesting since 1972’s peak of 74% of all commerce on earth it has declined to the last figure that I saw which was in the low 60%s.
The second part of that equation is that the Saudis would roll those dollar profits into US Treasuries.
This provided a constant market for the USTs, AND it established a “need” to retain dollars in central bank reserves to allow for the international settlement.
The question that I don’t see many people answering is what is Saudi Arabia supposed to do with Yuan or Rupees? They will certainly use the Yuan to import stuff from China, but I think a lot of it will be converted into dollars and used to buy stocks, USTs, and other investments priced in dollars.