Not quite -- if you look at the history of the first Saudi state (in the 1700s) and later on, you will see that there is no central power in the lands conquered by the Sauds. There were and are myriad tribes and clans and the Saudis conquered them. Their capital is in the east Riyadh and surroundings but they have a power base in Mecca and Medina as well.
To conquer "Saudi ARabia" you just need to convince various tribes and clans to stop following the Sauds.(ok, and that's not simple)
Cronos, it seems to me that if you take the capital of Saudi Arabia, you become the defacto government those tribes still answer to.
Hussein could have promised them to leave them alone and let them do as they pleased much like the Saudis had. I doubt they would have argued with that.
Perhaps there are sect issues I haven’t figured in. If so then you may have a good retort.