Jesus was a prophet of God and he came to revive the true religion of God for the Jews of his age in order to make them true believers, sincere in their faith and righteous in their dealings with other men.
His followers were first called Nazarenes. The Nazarenes formed themselves into a community at Jerusalem and chose James, the brother of Jesus as their head. The Nazarenes strictly observed the Law of Moses, just as Jesus himself had done.
With the passage of time, especially after the expulsion of the Jews from Jerusalem in 70 C.E., the new generation of his followers began to idealize the person of Jesus rather than his teachings.
This tendency developed further as Christianity spread among the Jews of the dispersion and their gentile neighbors. These people came under the influence of Greek philosophy. So when they accepted Jesus as the Messiah, they soon transformed him into a Saviour and Redeemer upon the pattern of Mithra, Adonis, Tannuz, Osiris, etc.
The man who played the leading role in working this transformation of Jesus was Paul. He was well versed in Judaism and in the Mithraism and Alexandrian religion of the day. He carried over many of their ideas and terms of expression into Christianity.
Further development in Christianity look place when the author of St. John’s Gospel took over the concept of the Logos (Word) from Philo and made Jesus into the incarnation c f the Logos
Controversies about the exact nature of Christ and his relation to God the Father continued for the next two centuries. The Arians considered Jesus to be a creature and hence inferior to God.
The Sabellians thaught that Jesus was merely an aspect of the Father, and that God was Jesus and Father at the same time. Yet another sect, the Catholics, believed Jesus a distinct person but of the same substance as Him and equal to Him.
Finally in the fourth century Christianity became the official religion of the Roman Empire following the conversion of the Emperor Constantine. The Catholic version was accepted as the official Christianity and all other sects were wiped out by sword and fire.
The doctrine of the Divinity of Jesus was finally established as a dogma of Christianity, as expounded in the Nicene Creed. The doctrine of the Trinity became inevitable.
Thus over the years Chustianity went on changing and inventing new dogmas of the Divinity of Jesus, the Trinity, the Original Sin, the Vicarious Sacrifice, the Blood Atonement and new rituals called the Baptism and the Eucharist.