The current US Govt continues to see every thing through the "IRAN" prism - TBH the Saudis have got themselves stuck in the Yemen swamp (as the Egyptians did years ago) and can't find a way out - that's the trouble when you don't have elections to change the guys behind the policy
The Iranians are just doing what the US did in Afghanistan - a few missiles, some money and you can create all sorts of problems for the those in the swamp. No need to invade - just keep the pot simmering