They can't follow most lines of thought except the one they have developed as part of a fantasy. In particular, they cannot follow a line of cause and effect that goes: "Something happened to me, and that changed me." They don't understand this line of reasoning. Instead, they peck away at other things, a line of seemingly random statements, with which they make connections to their fantasy. There is still a form of logic there, and you might be able to discover it, in retrospect, but it has nothing to do with the amount of data that was presented to them, or its contents.

I'm not sure what is currently going on with YouTube's closed captions. Is there a specific question you want answered? Basically what I was suggesting is the you can employ a strategy of saying and doing a range of things. It is like laying down many trails of bread crumbs. in the end, the narcissist follows only one line out of all of these you may have laid down. Their hints and remarks can suggest which line they had been following.