Christianity actually started before time began.
All that has played out so far in the history of the universe is part of the plan. As to what the end of the plan will bring, well, I can guess, but my little mind just cannot fathom all that God has done, is doing, and will do.
Prophecy of Christianity appears in the old testament more than 400 years before the birth of Christ. The house of David was going to bear this Earthly Savior. The Jews had been expecting their Messiah for centuries.
Evidence that Christianity was upon us appears when Jesus was a boy. I recall the instance where He was travelling with his parents, and did not join up with the caravan as it was departing. Jesus was assumed to be with other relatives in the group, so was not discovered to be missing for two days.
The family had to go back to the city and get him. He was found in the Temple, talking with the religious leaders there. And he was amazing them with his knowledge of scripture and God's Word. He simply told his parents that he "was about His Father's work".
The Church, as we know it today, was born 40 or 50 days after the Resurrection, on Pentacost. The Holy Spirit descended upon the Disciples, and they began to speak to a crowd of people of many nationalities. Each person present heard the words in their own native language.
They told the crowd that Jesus truly was the son of God, and that it was a BIG mistake to have crucified Him. They then advised the folks to seek forgiveness, and told them what God expected them to do.
Many people followed the instructions, and the Church grew very quickly. Years later, the followers of Christ were becoming well-known all over the world. In one city, Antioch, the congregation of the Church there was called "Christian" and the name stuck.
For 600 years the Church was just the Church, with a "nickname" of Christian. The Roman government was getting tired of all the religions of the day, some pagan, others were these darned "Christians". They tried to combine them all into a universal religion. CATHOLIC is the word they used, because it is a form of a latin word for Universal.
Later on, the Christians parted from the CATHOLIC group, but kept the name, and some of the structure. The brought back more of the Bible.
This was not enough for some groups within the new Catholic Church. The groups complained of too much "other stuff" carried forward from the other religions. They protested quite a lot, and eventually formed their own church that became known as "Protestant". Even within this Protestant group, factions disagreed on doctrine and tradition, so many sub-groups formed. Today we see Lutherans, Baptists, Methodists, and many others all coming from the Protestant Church.
But, even through all of this, the original Church never disappeared. It kept meeting, and kept growing. Today we see many such "non-denominational" churches that follow the structure outlined in the Bible. These are typically churches that do not have leadership beyond the congregational level. The bible does not provide for any such leadership beyond the local congregation, just Deacons and Elders, but they have no authority beyond their own congregations.