Complex sentence: Those differences were contributing factors in the separation of the two churches around 1054, but the formation of the canon was largely complete (fully complete in the Catholic view) by the fifth century, six centuries before the separation.
Split into simpler sentences: Those differences were contributing factors in the separation of the two churches around 1054. But the formation of the canon was largely complete (fully complete in the Catholic view) by the fifth century, six centuries before the separation.