Weren't land attack cruise missile airframes recovered? If you conduct a little research into Iranian missile forces and their disposition you'll find that it took them years and years to successfully reverse engineer, field, and integrate missiles they acquired from North Korea and China. I personally don't believe the Houthi have the ability to carry out such an advanced program without major assistance or Iran to outright conduct the attack. Can you even launch that LACM from the ground?

KSA use Patriot missiles for air defense, and they are notorious for having to be oriented towards the threat. If KSA suspected Houthi attacks as their normal defense posture, an attack from Iran would catch them off guard.

Additionally, the range of the weapons employed don't even allow for the consideration of a Houthi-led attack from Yemen. Look how close Abqaip is too Iran.

Source: intel analyst/Iran issues