For Zhou Tian, advancing his rule cultivation level wasn't exactly easy, but if that was his sole purpose, the task wasn't particularly difficult. He believed that if he left this world to make some preparations, even if he had to rebuild his rule cultivation level a hundred times over, for him, it would merely be a matter of time.
The real reason Zhou Tian stayed in this world was not primarily to enhance his rule cultivation level; for him, the main aim was actually to weaken the strength of the living beings.
At that time, for Zhou Tian, enhancing his own strength could be done at any time following the rules of the present world, but before that, he needed to first eliminate the obstacles that he faced in the world. And from any perspective, those living beings were definitely a major barrier for Zhou Tian; without significantly reducing their strength, the idea of turning this world into his own backyard was clearly a rather challenging task.