The Byzantines had for a century or two been persecuting Jews and “heretical” Christians all through the Levant, Egypt and North Africa.
For most of these people, the switch from orthodox Christian to Muslim rule really was an (initial) improvement, economically and for religious freedom, etc.
1500 years later it hadn’t really worked out that way.
Spain had also been indulging in religious persecution of minority groups, who reasonably enough felt little loyalty to their persecutors.
It is interesting that Muslim expansion more or less ran into a brick wall and stopped for centuries when it bumped up against united Christian populations in Italy, France, Anatolia, etc.
Obviously, if worship of Jesus as the Son of God was acceptable to “Moslems” then it would be an easy leap from defender to plunderer of the trade routes.
Not really. The majority of the Spanish population was Orthodox/Catholic while the Visigoth rulers were initially Arian. This wasn't a big gap at the time the moors came over.