People kept saying this movie was about faith but it's about an adult child healing from their abuse. His mother was part of a cult run out of their basement which led to his father's suicide. She abused her child with horrible "games" testing his faith. He chose to leave at some point. His experience that night was him dealing with the trauma. The angels are supposed to be protective but they're shown to be sinister and creepy which represents what people who suffered child abuse at the hands of their parents go through. We struggle with the idea that they are our parent and we should honor them so we should put up with whatever they do or forgive them for anything. But they were also supposed to protect us and they failed. His experience that night is PTSD, going through and dealing with his childhood trauma triggered by his memories of his childhood and the fact that his mother was fucking creepily obsessed with him. In the end, his choice not to believe is him reaffirming that he made the right choice to leave and he's ready to move on with life.