In the History of Christianity classes I had taken, multiple interpretations really took off once Christianity became Rome's state religion.
Fundamentally, Christianity "according to the teachings of Jesus" was simplistic. We started to make it complicated by trying to define the essence, nature and spirit of Jesus, The Holy Spirit, et al.
For example, you had the Council of Nicea (325 CE) to define a Christian. Then you had the Council of Constantinople (in 381 then in 553 and in 680 CE) to define it more and then you had the Council of Chalcedon (451 CE).
I find it interesting that the Council of Chalcedon stated:
Following the holy Fathers we teach with one voice that the Son [of God] and our Lord Jesus Christ is to be confessed as one and the same [Person], that he is perfect in Godhead and perfect in manhood, very God and very man, of a reasonable soul and [human] body consisting, consubstantial with the Father as touching his Godhead, and consubstantial with us as touching his manhood; made in all things like unto us, sin only excepted; begotten of his Father before the worlds according to his Godhead; but in these last days for us men and for our salvation born [into the world] of the Virgin Mary, the Mother of God according to his manhood. This one and the same Jesus Christ, the only-begotten Son [of God] must be confessed to be in two natures, unconfusedly (Eutyches), immutably (Arian), indivisibly(Nestorius), inseparably [united](Arian and Apollynariam), and that without the distinction of natures being taken away by such union (Eutyches, Polynaros), but rather the peculiar property of each nature being preserved (Nestorius)and being united in one Person and subsistence, not separated or divided into two persons, but one and the same Son and only-begotten, God the Word, our Lord Jesus Christ, as the Prophets of old time have spoken concerning him, and as the Lord Jesus Christ hath taught us, and as the Creed of the Fathers hath delivered to us.
Everything I underlined and bolded were the people I added in that the creed was personally attack as those people had different interpretations. Even the early church writers such as Justin The Martyr were defined as heretics based on their beliefs.
Everyone ("heretics" included) used passages of the New Testament to define their beliefs. One of the biggest reasons why we have the definitions of orthodox religion today is because of the Emperors backing up the Bishops who concluded that their interpretations were right. One example we have in this is the Emperor's daughter, Hilaria believed that Mary should have been the Theotokos (Mother of God). The orthodox Bishops said that was wrong. It should be Christotokos (The Mother of Christ). The Emperor of Rome was offended that the bishops would disagree with his daughter. So in the Council of Ephesus, the Orthodoxy Bishops made it official that Theotokos would be the word. This became Orthodoxy because the Emperor's daughter wanted it to be so. Just like many other reasons why things became orthodoxy.