From a Protestant perspective, Catholicism was far from being the first Christ-based religion. In fact the whole reformation fiasco that took place in the ~1400-1600s was a reactionary movement that sought to return to older, original representations of the faith as portrayed in the time of the New Testament’s writing. This movement was fueled by a critical thinking process that spurred a return to the original texts of the religions, and a realization that Catholicism had much in both its rituals and its canon that was nowhere spoken of in the original ethos of the faith.

Sadly you are misinformed. Christianity, prior to the Martin Luther stuff, was already split into several groups: Catholics, Eastern Orthodox, and the Coptic Church are a few that come to mind.