He does not want to expose his daughter to what they are currently facing, he wants her to spend her childhood with glee, free from worry.
"We need to tell Banjo to prepare, I have to focus on destroying the influence of the will of the Divine Realm on the lower realm." Amethyst knows the plan.
They are going to use the new and weak will of the lower realm as the host for the remnant will of the Big Bang Universe.
As long as they succeed, their future development will definitely be skyrocketing but this is not something that they can easily achieve.
Without any enemy, the difficulty might not be high because of how powerful the remnant will of the Big Bang Universe is and how new the lower realm's will is.
But if they start fusing the two wills, not only will they gather the hatred and attention of the entire force of the Demon and Plunder Universes Armies but they will also anger the will of the Divine Realm.