Untrue faith
Karl Marx famously stated that "religion is the opiate of the people", claiming that the ruling elite used religion to subdue the proletariat into accepting their place in society, in the mines and in the factories, by convincing them that God had ordained their lot in life.
If they did not upset the social order, they, the meek, would inherit the Earth in the afterlife. If they resisted, they would be punished with eternal damnation for questioning the will of God. Countless suffered and died under this theocracy, waiting for a salvation that never came.