The Demon Race is a loose alliance, and without a clear realization of the threat posed by the human race and an understanding of the ruthlessness of their actions, the various races within the Demon Race would not easily compromise.
Only by truly experiencing skin-deep pain, truly seeing the danger of annihilation, and truly knowing there is no possibility of compromise and no way out, can the various races set aside past grudges when facing life and death.
Otherwise, for the Demon Race to truly unite is simply impossible; the grudges and hatred among the various races are actually no shallower than those within the human race.
Even to put it bluntly, if it were not for the threat of the human race outside, the loose alliance of the Demon Race would not have continued to exist; without the threat of the human race, internal conflicts within the Demon Race would immediately erupt, and it would not be surprising if they fought like dogs.
