God is One throughout the Old Testament and into the New Testament. The trinitarian concept has no solid ground to solidify itself as fact. It was simply an idea that developed out of early Christianity and was agreed upon the Council of Nicene in the 4th century. It was basically just a later idea that people arrived at.
The trinity has nothing to do with God's holy bible. Jesus or his apostles did not teach the trinity and neither did Jesus say "I am God".
1) Even according to the Trinity doctrine, God is still
one. Now you're twisting the Trinity doctrine into saying something it does not say.
2) The Trinitarian concept is based upon both biblical and cultural tenet. That seems to be solid enough grounds for any other theological construction. Why do you hold the Trinity doctrine to higher standards?
3) It was not a "later idea." While it was not fully developed, there was always some idea that Jesus was -- in some way -- Divine, if
for no other reason than Luke's birth narrative, which mirrors that of Augustus in nearly every way (who was seen as a god by Roman Gentiles).
4) It isn't "God's" holy bible. It is
our holy bible. Once again:
a) The bible isn't the sole method of revelation
b) Teachings don't have to be explicit; they can be
implicit, which is the case here.