Soldiers don't move until supplies are ready.
This saying applies just as much in the Cultivation World.
Spiritual Energy Resources are the supplies of the Cultivation World.
In Wei Cheng's plan, the first priority in replicating the second stage of the Cultivation World is to prepare the storage of Spiritual Energy Resources.
However, truth be told, he didn't initially plan to replicate the Cultivation World. It was too daunting a thought. His initial plan was that of a bandit, taking Earth to another Cultivation World or Heavenly Demon World to scrounge for resources, returning whatever was borrowed—an ethically oriented strategy.
But then the Chaos Demon Star fell, destroying billions of Heavenly Demon armies in scant time. Wei Cheng happened to be plotted against by Immortal Gou Chen and during his struggle to free himself from the Demon Emperor's mark left by the Uninterrupted Demon Emperor, he conveniently benefitted a bit.
