Original: The origins of the taifas must be sought in the administrative division of the Umayyad Caliphate of Córdoba, as well in the ethnic division of the elite of this state, divided among Arabs, Berbers, Iberian Muslims (known as Muladíes - the overwhelming majority) and Eastern European former slaves.
Simplified: The reason that taifas developed was that there was an administrative division of the Umayyad Caliphate of Córdoba and also an ethnic division of the elite of this state. It was divided among Arabs (they werde a powerful but tiny minority), Berbers, Eastern European former slaves and Iberian Muslims (known as Muladíes (those were the great majority).