I am aware of the fact that Christianity was, historically, presented by oral means, ... actually from its founding to this time (for aome peoples of the world).
My point is that it should be readily understandable that the comprehensive view of JESUS we get through the scriptures (i.e. the OT plus Matthew - Revelations) was not wholly available to the early Christians, particularly those of the first century, during which time the writings of the NT did not exist, but rather, were actually in production.
Thus, the extent of a first century christian's view of Christ would easily (and most likely) be based on the testimony of one missionary/evangelist team, which, likely, would not supply the comprehensive picture of Christ we have today available in the scriptures.
Where are these "Missionary/Evangelist teams" in a Scripture that talks only of Bishops, Presbyters (Priests - look up the derivation), and Deacons?
And have you forgotten the Old Testament? "Then he opened their understanding, that they might understand the scriptures." (Luke 24.45). Surely, the Apostles their fellow members of the hierarchy would have used the widespread availability of the Septuagint to explain the faith to them as well? How could this not be a comprehensive picture of Christ? Are you claiming their preaching was lacking?