In the mainland, powerful beings like Zhou Tian might not be plentiful, but they are not entirely absent. And Zhou Tian knows to seize opportunities to expand his power, as do the monsters.
Although the Corpse Demons and Elemental Spirits have encountered many obstacles due to the resistance of the NPCs, it is impossible for the NPCs, with their strength, to stop the expansion of these two monsters.
As a result, the actions of the NPCs, despite having a significant impact in the early stages, were ultimately only capable of restraining the two monsters, even when making their fullest effort. They had no possible way of halting the expansion of the two monsters.
Simultaneously, some monsters that had been secretly accumulating power for a long time also began a series of expansion actions.