Déjà vu is a phenomenon I have experience often throughout my life. I have even found places that I had years earlier dreamed of. What the mechanism is, how does it all work. I can't say. I do believe that our concept of time is largely a mental construct.
It was the Swiss psychologist Carl Jung who gave us the term synchronicity. Which he defined as events of meaningful coincidence. And it is just that. We ascribe our own personal meaning to it and it has to be viewed through that lens.
As for the authors who's stories played out later as real life events, we as non participants can only wonder. You'd have to talk to the authors themselves to get to the heart of it.