Oil is a fungible commodity, and they have to sell it to somebody to make money. They have not adjusted their production rates for us at our request for a while, and we have pretty much stopped asking, to say nothing of the fact that we should be getting off of oil ASAP. The enemy of my enemy thing was always nonsense. Iran hates us because of our interference in the region, and interfering in the region because Iran hates us is counterproductive.
Money makes sense as a motive for Trump, as he is easily distracted by money and shiny objects, but Biden, Obama, Bush, Clinton? They have been willing to walk away from money if the optics were bad enough. But when it comes to the Saudis, they fold like cheap suits.