Thing is they didn't spread it to the rest of the world or simply can't before the Industrialization-Colonialism era. They mostly stuck themselves to Europe, taking over the rubbles of the Roman empire where billions died physically and psychologically in the name of God and the church while the rest of the world were still human organizations where if the rulers get corrupt and people start starving to death they are instantly overthrown on the spot.
That we know of, atleast.
Thing is they didn't spread it to the rest of the world or simply can't before the Industrialization-Colonialism era. They mostly stuck themselves to Europe, taking over the rubbles of the Roman empire where billions died physically and psychologically in the name of God and the church while the rest of the world were still human organizations where if the rulers get corrupt and people start starving to death they are instantly overthrown on the spot.