The answer, quite simply, is that the only thing that can kill a god is an ardent devotee. The more “ardent” a devotee gets, the more limitations he begins to place on his gods. He starts telling people who his god is in great detail. He starts to tell people what god can do and can’t do. He begins the celebrity manager for his god, allowing him some actions but not others.
His god will be vicious and angry but if you even suggest that his god can be forgiving and inclusive, he will lash out with “god will never do that!”. He needs to be the one to decide what his god does, what his god’s reaction will to all things.
Like a controlling manager. He will not even talk to his god anymore, content in the knowledge that he knows everything there is to know about them because he has read what people thousands of years ago wrote about them.
There is no greater insult to gods than their most ardent devotees.