YHWH declares his unique glory in Isaiah, and creation marks the beginning of the world's existence rather than God's.
Isaiah 42:8; Isaiah 48:11; Genesis 1:1 are major backgrounds.
Jesus does not ask to acquire a glory he never possessed. He asks to be restored to glory he already had with the Father before creation.
This is direct first-person testimony to pre-creation existence and shared divine glory, making it one of John's strongest deity passages.