Even those mighty forces were not strong enough to have a hard fight with Zhou Tian now that he had grown up. However, when most of their strength was deployed in the Outside World, preoccupied with finding Zhou Tian's footprints, one could imagine that their strength at home was certainly very limited at that time.
Those living beings were only thinking about how to find and eliminate Zhou Tian, their opponent. They probably never considered how they would respond if Zhou Tian were to launch an attack on their rear.
According to the situation at the time, those living beings still believed that they had the upper hand. Despite having the upper hand, they expected Zhou Tian to hide. Even though Zhou Tian had gained an advantage before, those living beings still did not believe that Zhou Tian would dare to provoke them actively.