As you read through the Jewish scriptures you learn three very important things (among many). First, that God has decided to reveal himself to humans beings. He's been doing it from the very beginning (Genesis chapters 1-3) and certainly no one made him. Communicating with humans at all is a pure, raw, free choice by God.
A second thing we find is that God has revealed himself via history. We might prefer, in our theological fantasies (if there are such things), that God had imparted all of his truth in a single, dispassionate, abstract, crystal-pure burst of light. Instead what we know of God, his goals and plans, his moral standards, what he requires from us, and what we can expect from him have all been communicated to us through his words and actions on the 'stage' of historical events. The Bible is the inspired (i.e., written in a partnership of God and humans) record of those actions and what they mean. There was a time when the Bible had not been written, but there never was a time when God was not revealing himself.
Story TellingAnd third, we learn that in revealing himself, God told a story. There is a story arc to the Bible. It begins with God being the origin of everything. It tells about the humans he created to reveal himself to, their disobedience of God, and the fundamental disharmony that fell on the world as a result -- a disharmony later called "sin." The story goes on to tell of a great flood in reaction to sin, and then of a man named Abraham who was selected to live up to a unique commission:
"I will use you to blessall the people on earth."
(Genesis 12.3, ERV)
From there we learn of the nation descended from him with the same commission and how they ultimately failed and were crushed by foreign nations. But not before producing a singular King whose dynasty was destined to issue in a man who would rescue Israel and the world, deal with sin, proclaim a new law "written on people's hearts," and inaugurate the Kingdom of God. The one, in other words, who would finally fulfill that commission. As the 1st century neared this rescuer came to be called "Messiah" -- "the specially commissioned one," the man with ceremonial oil poured on his head, as was done to kings and priests. In Greek, Messiah is "Christ."
So when we say Jesus of Nazareth himself, in his own person, is the Christian revelation, we mean he is the climax of all that had gone before as God had revealed himself to humanity. Jesus is the spear tip of all God had been doing to set things right since the beginning of time. Or as St. Peter realized, he is, "the Messiah, the Son of the Living God,"
One Other Point
There is one other point: As Jesus went about doing his job as Messiah it became increasingly apparent that things said only of God or done only by God in the Jewish Scriptures, were being done and described of him. "Anyone who has seen me has seen the Father too," (John 14.9 ERV). Very early on the life and actions of Jesus were realized to be those of God. Messiah turned out to be much more than was even expected, and those who looked for him expected quite a lot.
I've pointed out previously that the vast bulk of the Apostle's Creed is just a summary of Jesus' life. There is a reason for that. Jesus himself is the revelation because his words, life, death, and resurrection are the best possible way to grasp what God is really like. He is the ultimate self-revealing of God.
After 50 or 60 years of turning this over in his mind St. John described it concisely, "No one has ever seen God. The only Son is the one who has shown us what God is like. He is himself God and is very close to the Father," (John 1.18 ERV).