God exists from eternity to eternity and beyond. A form of "spiritual energy" that's living and thinks.
He creates because he can.
Even Einstein said before the Big Bang singularity there was nothing. Black, dence, void, nothing, visible and using the Bible's words God said let there be light - and from ALL the illustrations of what occurred at the moment of the Big Bang singularity there was a burst of microwave, radiation light, would have been invisible to the human eye but light. Full of substances that would turn into what is visible today - planets, suns, clouds, gases, and Waters.
His essence is creating, bringing light and life to the dark, vast, endless space.
Humans on "earth" ( whose first name was probably Eden God's Garden) after the fall of the Angels seem to had been formed especially for judgment. God did tell man and woman to be fruitful and multiply and "replenish" the Earth.
If creation of man didn't happen there would be no judgment - life on Earth would have been uncursed.
If creation of the universe didn't happen it would still be total darkness in endless space.