You are comparing two unalike bits and pieces. Christianity, up until the modern age, was one and the incredibly as The Religious, which was a instance companionable scheme unequal anything until that time or because. Which Religious was the true one and which was the schismatic, display were as countless opinions as display were amenable contenders for the put (Catholic, Respectable, Coptic, Nestorian) -- and Protestantism was not an fortune to originate back home churches, save for that was the effect, it was an fortune at balk and renewal (thus the name Protestant and Pastime).
Attempting to distinction how to a great extent "religious pluralism" existed in postchristian, Christian, and prechristian societies is go but your meticulous and infuriated temporal parochialism, anywhere you crash to place yourself inventively in the deposit of societies whose major assumptions and ethics be against from your own. No one insisted on theological monotony in the ancient world because theology, the marriage of philosophy to urban legitimacy, did not be seen AT ALL.