Demonic infestation — the presence of bothersome demons — is common in the writings of historical Christianity, Mahayana Buddhism (especially Tibetan), and most other traditions. The assumed ontology explains psychological phenomena, especially those related to behavior and morals, and always as negative. In monastic circles and among the sayings of the desert fathers, any sin or a temptation to sin was often viewed as demonic in nature.
A world, a sky, infested with demons is a pitiless view of nature.
But perhaps it was less terrifying to think of evil as the product of outside forces than of the darkness of human hearts. We have witnessed horrors enough in society and culture to wish that humans are merely tricked into evils and have nothing to do with them otherwise