Then they would realize that originally, the Church was the Catholic Church with Peter as its first Pope. It was started by Christ. When the Protestant Reformation occurred in the 16th century, that is when other denominations started popping up (because people left the Catholic Church and started…
Actually…
Peter - if he actually existed because it’s entirely possible that he didn’t - is considered the first bishop of Rome, but he never would have been called “pope.” Several bishops followed in the early days of the Christian faith. The term pope didn’t come about until the third century and it was randomly applied to several bishops. The establishment of the idea that the pope title belongs to the bishop of Rome didn’t come about until the eleventh century, and it was retroactively applied to all bishops of Rome. (Kinda like how Romney retroactively retired from Bain.) And even then there was infighting and several bishops disagreed with several pope selections and declared themselves “popes.” We know them today as anti-popes.
Also, the idea that Jesus (who also possibly never existed) made Peter the first pope is spurious at best.
Jesus spoke Aramaiac, not Greek, so he would not have made a pun about Petros being the rock on which his church (ecclesia) was built. He also wouldn’t have used the word “ecclesia” (Greek for assembly) to mean “a building” because even in Greek that usage of the word didn’t come about until centuries after the time of Jesus. The bible is also contradictory as to whether the apostle Peter and the apostle Simon are actually the same person. Also, just after Jesus tells Peter he’s a rock, he calls Peter a Satan for suggesting that Jesus not allow himself to be killed. This all suggests that it’s a later insertion.
So when you say that knowing the history tells the whole story, that’s true, but only when you actually know the whole history.