Yes, Krakauer has an acceptable background to speak with authority on this subject.
Krakauer has an acceptable background to speak on the subject because he has scores of outdoor experience; throughout the book, he makes mention of his climbing adventures throughout the book. In fact, written a number of books and articles about his outdoor experiences (e.g. Into Thin Air). Other than that, he knows quite a number of outdoor experts. Furthermore, Krakauer seems to understand Chris McCandless because of his own experiences with his father.