Earlier quoted context omitted.
That's what the US troops are there for. The US needs the Saudi dictators to maintain their influence in the region.
Needed, past tense. US foreign policy used to be shaped around our need for Saudi oil, and IMO hasn’t properly adjusted to the fact that America is energy independent again. The realpolitik question now isn’t “how can I secure Saudi oil” But rather “what’s the least I can do to reduce any risk of terrorism”.
US foreign policy is shaped around making sure the whole region remains in conflict. That allows for more weapons sales, cheaper oil due to infighting, and excuses to intervene and have the military there.