How does this happen? John just discussed a subject that I've been thinking about for two weeks; The importance of point of view in a novel. So I'll build on his comments.
What started me thinking was an article in the book review section of the New York Times. Written by Elliott Holt in his Critic's Take column, the article was entitled "The Return of Omniscience." Holt was referring to the surprising number of recent novels featuring a narrator "who is conscious of everything and isn't afraid to say so."
As an example he used the opening sentences from Celeste Ng's novel Everything I Never Told You; "Lydia is dead. But they don't know that yet."
I can recall a time when this usage would have sent a creative writer teacher screeching down the hall way. "No, no, no. The writer is not God." But why not? 18th and 19th century novelists did this all the time. Frankly when this technique is well done I love this authoritative voice. I think it's especially effective for historical novels.
In John Corrigan's excellent post, he refers to The Art of Fiction: Notes on Craft for Young Writers. This is an outstanding book. Another books that is a classic and one of the best is Frances Fugate's, Viewpoint. It's very hard to find and someone "borrowed" mine (I honestly forget who) and never returned it.
Holt provides an excellent analysis for "The Return of Omniscience." http://www.nytimes.com/2016/09/11/books/review/the-return-of-omniscience.html?_r=0
John discussed the problems and advantages of first and third person viewpoint. As for me, I'm frankly curious about the reemergence of mix and match. We're happily and solidly in the head of the first person narrator and them wham! A villain described in third person but at such a close distance we are in his head too. But the "I" is gone. At that point, the voice, the viewpoint is technically a rather sneaky omniscient narrator. I think.
I'll tell you what I know for sure: Only the shadow knows the evil that lurks in the heart of men. Surely this old radio introduction was one of the most scary statements ever devised for the omnipotent voice.