Re: The Spanish
They did… At first. But it fell apart into lots of petty states pretty quickly. When central leadership was weak, local governors could declare independence and this get to keep all of the revenue from their lands instead of having to pay a portion to the central government. Plus being a small independent state allowed you to make sure that power would remain in your family, rather than risking you superiors replacing you with someone else.
The downside, as the descendants learned later, was that when Crusaders would come bearing down on you from the north, there was no massive army available to defeat them because there was no central government to furnish such an army…