Saudi are going to do what?
They can't lift a single ever-so-aristocratic finger to help Iraq, possibly by forgiving the huge amount of debt that they hold from the 1980s. But they can help stir up the situation and keep it chaotic.
The problem is that the Saudis believe they can do this with impunity, and the violence will not spill over to Saudi soil. The Iranians will not strike Saudi assets in the Gulf, nor arm the Saudi Shia minority to the level that they could cause problems for the Sauds, nor will Iranian armies take a hike around Kuwait and actually invade Saudi Arabia.
They believe that this magical immunity is because the United States can't afford to let anything really bad happen to them.
Does anyone with a grip on US domestic politics actually believe that, having withdrawn from Iraq, we would deploy so much as a rowboat to help the Saudis? Might be good for them to get kicked in the teeth, hard, by the Iranians.
As for me, I'm going to start hoarding oil.