Why do atheists think God-believers are crazy?
When someone believes they see things that aren’t there, we call that schizophrenic.
When someone hears voices that nobody else hears and thinks they are talking to them, we call that schizophrenic.
When someone believes in things that do not fit our observable reality without evidence or contrary to evidence, we call that delusional disorder.
When someone believes in magic and talking animals because it is written in a book, we call that delusional disorder.
When people harm others because they think it is moral, we call that psychopathic.
When people are eager to be done with life, we call that by a term that you can’t use on Quora without getting red flagged.
When someone thinks the wine and bread they are consuming are the blood and flesh of a dead person, we call that delusional/pathological cannibalism.
When someone thinks that they are being watched at all times, we call that paranoia.
When someone thinks there is an invisible evil being that is out to get them, we call that paranoid personality disorder.
When someone starts mumbling incoherently with their eyes rolling back in their head but they are not having a seizure, we call that delusional schizophrenia.
If someone fit just one of these criteria, we might call them crazy. Many theists fit all of them and all theists fit at least 5 of them. Theists are clearly crazy.