Bear with me while I conjecturalize (is that a word?).
Jesus is the Living manifestation of the written document.
John 1
[1] In the beginning was the Word, and the Word was with God, and the Word was God.
Rev. 19
[13] And he was clothed with a vesture dipped in blood: and his name is called The Word of God.
They, under the inspiration of the Holy Spirit, whom Jesus shares with in his triune nature, were writing about him the whole time, Old Testament, too.
Josh. 5
[13] And it came to pass, when Joshua was by Jericho, that he lifted up his eyes and looked, and, behold, there stood a man over against him with his sword drawn in his hand: and Joshua went unto him, and said unto him, Art thou for us, or for our adversaries?
[14] And he said, Nay; but as captain of the host of the LORD am I now come. And Joshua fell on his face to the earth, and did worship, and said unto him, What saith my lord unto his servant?
[15] And the captain of the LORD's host said unto Joshua, Loose thy shoe from off thy foot; for the place whereon thou standest is holy. And Joshua did so.
This would NOT have been just an angel.
Heb. 2
[10] For it became him, [Jesus, insert mine] for whom are all things, and by whom are all things, in bringing many sons unto glory, to make the captain of their salvation perfect through sufferings.
Furthermore, Jesus was not starting a "new religion." He was fulfilling and unfolding the "religion" (if you will) that was already in place. Christ came to open up the mysteries seen in types and shadows in the O.T. in himself.
Col. 2
[16] Let no man therefore judge you in meat, or in drink, or in respect of an holyday, or of the new moon, or of the sabbath days:
[17] Which are a shadow of things to come; but the body is of Christ.
He wasn't a mere man needing to vindicate his new "movement." This was God in the flesh testified to by witnesses.