The LORD did not introduce Himself by saying, “I am God most high, creator of heaven and earth.” Moses lived in a world that revered many gods, several of which might have claimed that title. Raised in all the wisdom of Egypt, Moses was familiar with the gods of the Egyptian pantheon. After forty years in the household of a Midianite priest, he had become familiar with the gods of Midian. “God” was a pretty broad term then just as it is now.
God identified himself to Moses as the God of Abraham, the God of Isaac, and the God of Jacob. That narrowed the field down significantly. By identifying Himself as the God of the patriarchs, the LORD distinguished Himself from the pantheons of clamoring fakes and would-be-gods of the world.
Moses had been nursed by his mother and had lived among his people. He was well-versed in the lore of his fathers, the stories of the God of Abraham, Isaac, and Jacob. From boyhood he knew the stories of the God who appeared to Abraham and made a covenant with him, but the stories only became a reality in his life as the voice from the bush declared, “I am the God of your father, the God of Abraham, the God of Isaac, and the God of Jacob.”
He said also, “I am the God of your father, the God of Abraham, the God of Isaac, and the God of Jacob.” Then Moses hid his face, for he was afraid to look at God. (Exodus 3:6)
The holy martyr Stephen says that when he heard these words, “Moses shook with fear and would not venture to look” (Acts 7:32). This was not some local deity or mountain god, it was the God Almighty, the maker of heaven and earth. Moses immediately concealed his face lest, in seeing God, he die.