I sincerely believe that Saddam's downfall was due to his attempt to have oil paid for in euros rather than dollars, and the European Union turned its back on him.
Gaddafi wanted something similar: he wanted to create an African currency backed by gold.
The most important thing for the United States is not oil but the petrodollar, that energy be paid for in dollars, maintaining the hegemony of the dollar, which allows it to finance its trade deficit by exporting inflation to the rest of the world.
Maduro sells oil for cryptocurrencies and other currencies other than the dollar.