How could boccaccio's explanation lead to distrust of religious authorities?

The Medieval people who were able to witness and experience the Black Plague believed that the disease came from God as a form of punishment. Boccaccio was one of those people who were able to witness the plague but he had a different belief about the disease. Many people prayed to God to spare them from the disease but Boccaccio, though his book, told people that the only way to escape from the disease was to run away. This undermined the religious authorities since it presented the possibility that God could not help the people.