Oversimplification, if not revisionist, IMO. Certainly, that plays a part, but I cannot fathom how either the divided Orthodox (or the even more divided reformers for that matter) could muster a naval force sufficient to repel the Ottoman Turkish fleet - more than once.
And, can it reasonably be argued that the division in Christianity was a factor in the Turks’ decision to attack?
Battle of Lepanto, anyone? 500 years after the great schism, and just as the “reformation” was raging (1571).
As to your purely historical argument: I always thought that God was in charge of all things.