Earlier quoted context omitted.
What prevented that from being possible before?
You needed airplanes, and antiaircraft weapons were so much cheaper. With drones the calculation is the other way around. It completely changes the face of war, offensive warfare is now possible again. Ernst Jünger said something similar when he witnessed the first tanks in World War 1.
You mean defensive. Where American firepower at the hands of Saudis completely fucking up your country can be finally challenged with a response that might make them reconsider war. Where it was just a beat down like America is using to doing.
Who knows maybe this thing spirals out of control and destroys all of Saudi Arabia, when you are dealing with these sorts of political realities you reconsider things like destroying the entire country of Yemen because you don't like the politics of its majority or its rebel government.