The USA made Saudi Arabia via Ibn Saud, and it will unmake it via Iran. The sanctions were lifted on Iran, because the USA saw the writing on the wall years ago about Saudi Arabia drying up. It needs to reposition itself as an ally of the next major middle eastern oil producer. Not only does Iran have oil, but it has some of the largest natural gas deposits in the world. [1] After years of conflict, and a proxy war in Yemen, Iran is likely to do anything to ruin Saudi Arabian. This means any power over production that Saudi Arabia used to wield via OPEC will be nullified once Iran is developed by Big Oil.
Its an end of an era. The war in Yemen keeps aggression pointed outward, but as soon as the populace tires and the payoffs stop coming it will turn inward. Another government will be recast as tyrants and despots, and the world will watch it fall.
[1] https://en.wikipedia.org/wiki/List_of_natural_gas_fields