Beyond their great strength, Behemoths also have another characteristic: flexibility. Otherwise, they wouldn't be able to suppress Giants, even if their strength wasn't quite as remarkable.
Another advantage, or rather a Talent of the Behemoth, was also revealed to Zhou Tian at that time.
Behemoths during combat are enormous, even though no one has truly measured them. But based on estimation, a typical Behemoth is no smaller than a Giant. In normal circumstances, the castles of ordinary living beings are mere Steps for Giants; a Giant with decent jumping Ability could leap directly into them from outside. It's clear to imagine, therefore, that Behemoths, with such a size difference, would find it challenging to live alongside regular Beastmen, whether or not they are truly blood-related.
It's not a matter of whether Behemoths would attack ordinary Beastmen, but rather if ordinary Beastmen could adapt to living near Behemoth Clans.
