You answered the first part, as what are the problems related to it, now admitting that the arab class keep being a martial one, that the Caliphs manage to ease the tensions, and reform the army Al-Hakam have his son earlier and alienate Al-Manzor, and let's be generous, by 1070 the caliphate is still standing, the Fatimids are gone to Egypt, and the Almoravids just came in, and pledged allegiance to the Ummayad Caliph, now, what happens ?