How did the Umayyad Caliphate lose power?

Answer 1

It depends on which Umayyad Caliphate you are talking about.

The Umayyad Caliphate in Damascus from 660 C.E. to 750 C.E. was overthrown by a coup d'état led by the Abbassid Family.

The Umayyad Caliphate in Cordoba from 711 C.E. to 1038 C.E. ended when the final Caliph, Hisham III, died without any successors.

Umayyad Caliphate in Damascus
In the Umayyad Caliphate in Damascus case, there were a few major issues.

1) Mawali: Mawali (or non-Arab Muslims) were traditionally excluded from political and social affairs. The Umayyad in particular treated them as second-class Muslims. The evidence of this treatment was that Mawali were not allowed to have many government positions and that they were taxed whereas Arab Muslims were not taxed at all. Mawali made up an important component of the Umayyad Caliphate, especially Persians. Persia was always a high seat of culture in the Islamic Empire. As a result, ideas moved quite freely throughout Persia and Persians considered themselves to be of equal worth to Arabs.

2) Shiites: Under the Sunni Umayyads, Shiites were also discriminated against. After Yazid I martyred Hussein, the Shiites made it their mission in life to oppose every action of the Umayyad dynasty. It did not help matters that the Umayyads tortured and murdered Shiite Imams and Infallibles, leading to irreconcilability between the Shiites and the Umayyads.

3) Distance: There were no effective routes of communication between the Western Edges of the Caliphate and Damascus. This made local administrators more powerful as they would have to make their own decisions anyway (it would take too long for a messenger to go to Damascus and return). Many figured that they might as well make the change more permanent.

4) Political Issues: Not all Arabs of high political standing supported the Umayyads. There were several other families that were just as power-Hungary and the Umayyads spent much of their time thwarting coups d'état. Abu Al-Abbas As-Saffah of the Abbassids rose against the Umayyads and murdered the reigning Umayyad Caliph. He ordered the rest of his family to murder every single other Umayyad. As a result of the uprising, only one Umayyad, Amir Abd El-Rahman, survived. He would later flee to Spain and set it up as a Caliphate in opposition to the Abbassids.

Umayyad Caliphate in Spain
There were really only two issues here.

1) Christian Victories: In the mid-800s, the Umayyads in Spain arrived at a turning point. A massive number of Christians were beginning to immigrate to the weak Christian Kingdoms of Leon, Castille, the Basque Provinces, Aragon, Navarre, and Catalonia. Many of the Christians came from France and Germany and brought more recent European technologies with them. This led to the successes of the Reconquista in the late 800s and early 900s. By 1038, King Alfonso VI was ruling the Kingdom of Castille-Leon from Burgos and had El Cid (a famous Spanish general) conquer the Umayyad bastion of Toledo. These Christian victories strongly weakened faith in the longevity of the Umayyad project.

2) No Heirs: The Umayyad Caliph Hisham III had no heirs. When he died in 1038, there were no longer any Umayyads left to succeed him and continue the line. He did not style a soldier or bureaucrat to be his successor and regional governors claimed regional authority, resulting in the first Taifa Period of Andalucía.