The cardinal’s death is associated with Finch’s mental illness in his memories. What’s notable about the cardinal is that Finch asked his parents for help—and they refused to help him keep the cardinal safe. Now, as a teenager, Finch still doesn’t feel safe asking his parents for help. They’ve shown him that they’re not going to support him or try to keep things from dying. So, without them, Finch has had to come up with insufficient coping mechanisms to deal with his mental illness.