I can't say about Saudi Arabia, but in general across the developing world, the people who inherited power from the colonial masters were either connected to or influenced by said colonists. There was no real dismantling of the old power structure; it only changed shape and character.

Unless that original power structure is dismantled (a tough task since those in power entrench themselves against any insurrection), you can't fully say what a country's growth trajectory could have been. Botched though the surgery may be, the former colonies still seem to be connected to the colonists in some way.