The arrogance and prepotence of the masses of followers among them, made them lose the truth. And whenever a messenger is sent, to be among them, to help them rediscover this truth, and they reject him, because of their dogmas, they succumb even deeper into this abyss of ignorance.
This is the biblical hell. It is not a hell of fire and creatures with horns, but a hell of spiritual suffering, caused by ignorance.