Because if defeated, it indeed signified that they were truly inferior to the other party. Although ignorant of the principle "victory belongs to the powerful, while the defeated are wronged," monsters innately held the concept of submitting to the strong. Once they were defeated by enemies, they would develop a sense of fear towards them. Additionally, defecting to higher-level monsters wouldn't severely weaken their own strength; at most, a reduction in power was a consequence that they could accept with not much difficulty.
After all, compared to a bit of power, life is definitely more important. In circumstances where everything is weakened, it's possible that, driven by their pride, the monsters would have fought Zhou Tian to the end. But with only some power lost, Zhou Tian was confident in the possibility of the emperor-level BOSS's capitulation.
