Why was spain a relatively easy area of europe for the muslims to conquer?

Islam in Spain has had an important incidence in the culture and history of the nation. By the time 'Abd al-Rahman get hold of Spain, the Arabs from North Africa were already rooted on the Iberian Peninsula and had started to write one of the most magnificent chapters in Islamic history. It is normally held that the relative ease that the Arab/Berber armies dominated the Iberian Peninsula with was due to the centralized nature of government under the rule of the Visigoths. The invasion of Spain occurred due to the expanding of Muslim influence in the North of Africa and the destabilized state of Visigothic Kingdom due to civil wars. It is also thought that Muslims were requested to invade Spain by one of the feuding parties.