There Is a Kingdom in the Core of the Earth

Why do humans on the surface of the earth want to finally achieve the unification of all mankind? Do humans in the Earth's core exist as "gods"? Why do humans in the core world and humans on the surface live in good neighborliness? As the earth's vitality weakens and ages year by year, humans in the core world and humans on the surface world, why do humans in the core world go to another planet to develop together with people in the surface world?