Islam is an anti-Christian movement. You have just detailed how disunity has enabled the rise in our day of the worst threat to Christianity in our world today which is perpetrating the worst persecution of Christians today.
Heresy should be so lucky.
in sotuhern Iraq at the time of Mohammad, the Sassanids and the Romans were fighting each other through their Arab proxies -- the Ghassanids were Christian Arabs and the Laksmids were Zoroastrian.
Mohammad took the Gnostic, ARian beliefs he had heard along with Jewish beliefs (Medina was a Jewish town originally) and merged it with Zoroastrianism and ancient Arab polytheism to create a uniting force for ARabs
The Wahabbis are trying to do the same.