“Game Night” featured the return of Nick, who was sprung from prison by demons interested in getting Lucifer back.
Lucifer is, of course, in The Empty, but Nick devised a way to spring him.
Well, the guy has been severely unbalanced for a while thanks all the years being possessed by Lucifer and the murders of his family, and he decided that the only way to get his son back involved bringing Lucifer back.
Nick is just crazy enough to get violent in order to do it.