In the first few centuries after the death of Jesus many different sects of Christianity rose up. The orthodox church from constantinope, and the Roman Catholic church in Rome became the most dominant. At the council of Nicea, one bishop from Alexandria did not sign the Treaty. This bishop was named Arius. The did not believe in the Trinity doctrine, so he was proclaimed a heretic. He had a decent number of followers who went on missionary journeys into eastern germany. Many tribes converted to these beliefs which would come to be known as Arian Christianity. Some notable tribes that adopted these beliefs were the Visogoths, Ostrogoths, Lambards, and the Vandals. Through a series of events the Vandals landed themselves in northern africa, the breadbasket of the Roman Empire. They captured Carthage and made it there capitol. They gained recognition from Rome as the kingdom of Vandalia. Through the short existance of Vandalia they pillaged and waged war with Rome and the Byzantines until finally being destroyed by the Byzantines during the rule of Justinian.
The scenario I want to develope is what if the Vandals survied the reign of Justinian, until the Byzantines stopped trying to reunite Rome. I had an Image of the Vandalian Empire, spanning across north africa. I see it going from the west coast of Modern day Morrocco to the Nile at its greatest height, sometime around the First crusade. I also imagine the Vandals establishing an Arian church in the empire. There were a good deal of them when they first arrived, and the vandals were notorious for their brutal tactics, which would gain a stream of forced conversions, alowing the Arian church to grow. I imagine the capitol of the Vandalian Empire being in Carthage, and the center of the Arian church being in Alexandria.
How plausible is this scenario? If this scenario is at all plausible, how might this effect the spread of Islam? And what impact might this have on the crusades?