If Dahmer was an atheist, why was he constructing an altar that he imagined giving him new power?

From 'The Shrine of Jeffrey Dahmer'; “He still nurtured the idea of his own temple, and these were steps towards its realisation: the black table would be the altar, and the griffins, mythological creatures with the head and wings of an eagle and the body of a lion, would be its protection.”

Maybe consider that people say things at different times for different reasons, and what's true is what they do. The world will make more sense.