It's untold true story the author was never privy to. It's what Lincoln told his wife and never told anyone else, and told her with curiously curated story beats and concluded with a great sensitivity to how people would reenact it for a punchy film centuries later. It's what Nixon really regretted. It's what truly tempted Christ last.
It's based on real events you don't know well enough to disbelieve. It's a ghost story, it's a war story, it's a once in a life time love story that will somehow be told in ten different movies this summer by ten different ensembles.