Christian princes were in Spain long before the Muslims got there or before Islam even existed. The only good result of the Muslim invasion was probably the unification of Spain, because the kingdoms finally had to unite in order to drive out the invaders. It wasn't easy, because many of them had worked out accomodations with the Muslims (the king didn't mind giving away a certain number of young subjects every year) and many of them hated each other even more than they hated the Muslims.
The alliance between Aragon and Castilla was the final result of gradual consolidation, with one of the reasons for this being the increasing resistance of the Christian kings to the Muslim raiders.
Interestingly, Christianity in Spain had been infected by Arianism, which is certainly the heretical form of Christianity upon which Mohammed based some of his delusions. It was essentially a religion that regarded Jesus as non-divine but important, although ultimately just another leader or prophet. Sort of like today's Unitarians.
The Visigoths were Arians. After Ricaredo renounced Arianism and became a Catholic, which was the religion of most of the Spanish people (in contrast to that of the Visigothic ruling class), the Spanish kingdoms began to form a more consolidated front. However, the primary reason that the Muslims were able to get into Spain in the first place was that they were hired by one Spanish Christian king to attack another. This should be an object lesson to us all, although I doubt that it will be. Certainly not to the Europeans, who hate us so much they would form an alliance with the Devil himself if they knew how to send him an e-mail.
Spanish history is exceedingly complex.
The Umayyad Dynasty initially established a unitary state in Spain after mopping up the lightly populated Visigothic kingdoms as almost an afterthought. That state eventually devolved into a series of kingdoms.
The North, unconquered by the Moslems since it was, economically, a disaster, was reorganized by a foreign invader from CORNWALL, not Spain since the Spanish aristocracy didn't survive the Moslem conquest.
Along the way a second Moslem invasion occurred in an effort to drive out the Christians who'd successfully penetrated the Islamic South, and to re-establish the unitary state.
They succeeded for a while.
As the Kingdom of France pospered and dragged itself out of the Dark Ages they began providing serious numbers of mounted knights for use in the various wars in Spain.
I suppose some native Spaniards might well have joined the French and Cornish, but there was always a cheaper source of soldiery among the dispossesed in France.
After reading a gazillion books about the history of Medieval and Islamic Spain over the years, I have yet to find a reason to credit the native Spanish population in the South any credit for eliminating Islamic rule. Rather, they seemed to enjoy it.