Many fossil fuel companies, especially ones involved in the middle east petrostates gain huge oil rent from selling oil.

Basically, the price of oil is close to the price of producing it in the "marginal" fields (the least productive fields), while some oil fields are many times more productive than the marginal fields. The owners of the hyper productive fields gain huge amounts of revenue from selling oil (this is called "differential rent" in economics). And this profit comes from owning the oil fields themselves.

If the demand for oil were to fall, its price would fall quite rapidly, as oil producers would abandon low productivity marginal fields. This would torpedo the oil rents of the petro states

This rent effect exists for lots of goods, but it is more pronounced in oil because oil is a scarce natural resource that is spread very unevenly.

On the political side of things, the oil rent of the big producers is protected by the US government, because the oil rent of the big producers is what holds up the value of the USD.