I don't think that a smart person suddenly starts to fear AI risk because they read in a newspaper that Steven Hawking is afraid of it.

Well, Steven Hawking is far smarter than most people, so on most subjects which Steven Hawking is familiar it would be a good idea to update in the same direction as him, unless you are an expert on it too.

Also, it raises AI risk as a possible concern, at which point people might then try to find more information, such as Bostrom's book, or website.

So yes, people get more information from reading a book than reading a newspaper article, but the article might be what lead them to read the book in the first place.