The filmmakers are trying their best to sell the viewer the idea that the film is about trauma and grief experienced by normal people. Therefore, main characters' actions are dictated by their loss. They're not. The film is about a disfunctional couple of two narcissists going through a loss. They didn't care about each other or anyone else even before the death of their child. The death only shattered a fragile balance and triggered destruction of everything and everyone around.