General Discussion

could not possibly have been accomplished by humans alone.

First Jesus' teachings and events had to happen. Then his disciples got turned into Apostles on Pentecost, the day that Jesus poured out his Holy Spirit upon them. After that, the churches had to be established and coordinated. You can read about those years in Luke-Acts, which follows immediately after the Gospel of John.

Luke, an historian (also known as 'the evangelist') accompanied Peter and Paul to Rome, and wrote both the Gospel of Luke, and the "Acts of the Apostles,"
-- about Peter, James, John, Paul, healing the sick as Jesus empowered them to; of their various miracles (which Jesus empowered them to, and the Church Fathers decided miracles qualify anyone for sainthood)
-- how Peter raised Tabitha from the dead, Philip taught the Ethiopian chief minister to the Ethiopian Queen Candace and baptized him; Paul (who was once the persecutor of Jesus' followers) then raised a young boy from the dead, and he recorded their amazing sermons in Acts, etc.

Then they had to become bishops of the first churches, and when doctrine got misunderstood, they referred to Peter in Rome who, with John, traveled to the new churches and settled doctrine questions of their churches' converted Jews, Greeks and Gentiles' questions.

Then they of Jesus' inner circle -- Peter, James, John, and Paul -- along with Matthew and Luke, had to write the words and deeds of their Lord in the Four Gospels and the Letters from the Apostles.

So a lot went on in the first 100 years after Jesus' death (witnessed by John and 3 Marys) & resurrection, witnessed by over 500 along with the Apostles. Then after 11 of the 12 Apostles were put to death (only John died a natural death in 99AD) the New Testament of their words and deeds got put together by their appointed successors known as the Church Fathers, themselves also bishops (and the Bishop of Rome, Peter's successor, since called the Pope, the word which means earthly "father."

To your opening point... there was no hierarchy except in Apostolic succession. The bishops and ordained priests (who also have a long biblical history)who the apostles chose to succeed them, shepherded their flocks, spread the Word, and humbly guided people to more spiritual lives.
Finally, it wasn't humans. It was Jesus himself who said, "You are Peter, the rock, and on this rock I will build my church" -- he didn't say Peter or any of the apostles would build the church; not the rest of humans who Paul called "the body of Christ" -- they were just his servants. The last 2,000 years haven't been easy (martyrdom, holy wars, etc., etc.) without joy, humility, and most of all, the Holy Spirit, which is the spirit of Jesus.

And whatever was the point. That is what Jesus built his church to tell you. And it's not complicated.