The Saudi Monarchy is pretty radical already. They promote Wahabi sIslam all over the world, as an outlet for the repression of their own population, the 99% that aren’t members of the ruling family. The Saudi Royal Family is not radical any more than the Shah of Iran was a radical. As someone who lived in the Kingdom for five years, whoever replaces the House of Saud will be far more radical and inimical to our interests.
If they lose their oil revenues, we will have to step up and get out own oil out of the ground. Any radical Islamists that take over there are not guaranteed to derive revenues when they have Iran and the Russia to contend with.
All oil is fungible. Saudi production will go into the global pot. The Saudis have the largest reserves of exportable oil.
The Saudi Royal Family is not radical any more than the Shah of Iran was a radical. There are members of the Saudi Royal Family who are very big supporters of radicalism. Not every Wal-Mart heir is a whinging lefty, but some are.
Far more importantly, the Saudi Royal Family has spent many billions of dollars exporting radicalism as a means of appeasing the forces of radicalism at home. So long as money was flowing they found it a lot easier to pay a wanna be Wahhabist Iman to go found a Mosque in Pakistan, or Algeria, or Germany, or Pennsylvania, and stay there, than to kill him, and risk the wrath of his kin and fellow Wahhabits. In the long term funding radicalism will surely prove fatal to the House of Saud, but for a couple of generations it has allowed Saudi princes to keep enough of the oil revenue for themselves to sate their appetites for blondes, blow and Bugattis.