Why are so many of the True God Churches spread all around... It's not because they have a conflict with the Holy Mountain, but because the priests of the True God Churches have always been the main force against demons.
The True God Churches and the Abyss Forces are utterly irreconcilable.
If it were just ordinary hybrid demons, so be it, even if they inherited the blood of a demon lord from the Abyss, so what?
There are plenty of such existences with demon blood, should they all be eradicated?
So clearly, this is not how things are calculated.
What truly stirred a reaction among so many of the members of the True God Churches was the blazing flames that once burned on the Holy Mountain.
Many elders in the churches fell in that battle, due to the Abyss Gate opened by the Succubus Queen and the preceding Dawn Saintess, fighting to the death against many Abyss Creatures.
