“WTF? The Saudis have AWACS! We sold it to them. Put 2 of them up, along with 100 fighters, for a week straight to keep anything else from getting through.”
Because they also suck at CAP (combat air patrol) and C4 (command, control, communication, coordination). If they were even minimally competent, they’d have caught slow-moving drones and relatively slow cruise missiles well away from any strategically important sites, like maybe oil refineries making up HALF their refining capacity.
Even if those drones and cruise missiles were flying nap of the earth they could have been detected. But the Saudis suck at both the offense and the defense, so there’s always that to consider... ;-)
Time to open a manual perhaps? Boeing tech support?