I think this book needs to be viewed at the Cosmic level. Let's view it from the stratosphere where we can see all these little insect characters with their mountainous egos behaving as if they can make a difference in the world.
Ophelia:Can you explain what you mean Kenneth?
Well, I think the author is willing to suspend plausibility in the day to day nuts and bolts part of the story in order to emphasize big themes. In the quote that you have highlighted I am alluding to the theme of Fate vs. Free Will which is everywhere in the book. Individuals tend to inflate the importance of decisions in their life-- not that they can't be important or even momentous, but in the grand scheme of things the choices we make take place within circumstances that are pre-determined. I think McCarthy sees human beings as tiny specks swept along in the tidal wave of events and history.
Example: Llewelyn Moss makes a momentous decision when he decides to keep the bag containing 2 million dollars. But how many hundreds, thousands, millions of events and circumstances had to take place over numerous lifetimes to put that money under his nose? He may have overslept and not been able to hunt that morning. His wife may have been feeling ill, his truck may have malfunctioned. The drug deal could have been resolved satisfactorily..... a thousand things, completely out of his control, could have kept him out of that Mexican hospital. If the wounded man who begged for water had been shot dead (a bullet one-quarter of an inch to the left or right), Moss would not have returned to the scene-- what then?
The Fate/Free Will theme is not just woven into the story. It is discussed openly between characters in a number of scenes. Maybe it's me, but the word "luck" seems to be all over the place.