Why is Christianity so divided when Christ established just One Church?

Answer 1

For the purpose of this Answer, there are five major sects in Christianity and some say even more, but the easiest way to break up Christianity is into these five categories: Orthodox (referring to the Churches of Eastern Europe), Catholic (referring to the Church led by the Pope), Protestant (referring to the Churches of the Reformation and beyond), Eastern (referring to the unrelated Churches of the Middle East, the Caucasus, and Ethiopia), and Mormon.

As to the actual question, its premise is incorrect. Christ did not establish the Church, Peter and Paul started the Church. By the time that Jesus died, many of the key beliefs about Christianity had not yet developed. Some of these beliefs, that would be articulated later by the Gospel-Writers and by Paul in the Epistles include: Christ's sacrifice for humanity's sins, the nature of the Trinity, Jesus' complete humanity and complete divinity, that the God of the Old Testament and the Father of the New Testament are the same God, etc. These things were established by Peter and Paul and other church leaders in the early days of the Church.

One of the major misconceptions that Protestants (typically) have about Christianity is that they believe that the New Testament was written and then the Church formed. The reverse is true; the Church wrote the New Testament. What went in was what they could agree on. However, some of the more complex concepts discussed above were not agreed upon by all consituents to those Councils. The Eastern Churches left the Church earlier because of disagreements at these council meetings. The Orthodox and Catholics split up over the hierarchy at further councils to determine the trajectory of the faith. The Orthodox believed in a community of equal patriarchs representing the various dioceses. The Catholics believed that a singular heir to Peter, the Pope in Rome, should be authoritative in guiding the church.

When the Protestant Reformation went on in Western Europe, many Orthodox were hoping that these new non-Catholics would "revert" to Orthodoxy. However, Lutheran and Calvinist groups rejected both the singular authority of the Pope and the communal authority of the Orthodox. They rejected a unifying authority of any kind. Without a council or leader to unite the various factions of any Church, the Protestant churches continued to splinter, because as soon as there was any sort of theological disagreement between Protestants, there was no way to reconcile it. Additionally, having a much stronger "faith" component in most Protestant denominations led to Protestantism being much more flexible in adapting to individual communities' needs. It could be "raging hellfire" type preaching or "walking in the garden" type preaching, allowing groups in brutal and peaceful situations to create their own Protestantisms. It is worth noting that Protestant denominations which have preserved an authority figure or the traditional church structure, such as Anglicanism and Episcopalianism have not split the way that other Protestant groups have.

Periodically, there have also been nationalistic divisions between the Churches. The Episcopalian Church split from the Anglican Church out of loyalty to the nascent United States over the former British Colonizers. The Slavic Orthodox Church of Bulgaria split from the Greek Orthodox Church to represent the Bulgarian national identity as opposed to having solidarity with the Greek national identity. (The Greek Orthodox Church was closely tied with the Greek Independence Movement which had territorial goals antagonistic to the Bulgarian Independence Movement.)

The Mormons split from the other Churches because they believe in additional testaments.