Zhou Tian indeed would not abandon the assistance of the Beastman Tribe unless it was absolutely necessary, and at that time, if those forces threatened the safety of the Beastman Tribe, Zhou Tian would undoubtedly drop everything to come to their aid. But now the question is, did those forces actually pose a threat to the safety of the Beastman Tribe?
No matter what those leading forces were thinking at the time, in any case, as they were not exerting their full strength, Zhou Tian's Beastman Tribe has remained safe and sound up to this point, having encountered no danger.
Thus, even if Zhou Tian was reluctant to give up the assistance of the Beastman Tribe, with the Tribe facing no actual danger, he naturally would not abandon the tasks he had already started over some battles. Moreover, those forces at that time probably vastly underestimated Zhou Tian's determination to deal with that Human Emperor.