The reason is not down to native intelligence, nor talent or dedication. It isn't that one person wants success and the other doesn't. The difference lies in what each person knows and how he or she makes use of that knowledge.
That is the whole purpose of the book: to give you knowledge - knowledge that you can use to navigate the challenging road that 90% of applicants stumble and fail on so that you can fast-track your way, with ease, to a glamorous career with your chosen airline, that will take you to exotic countries and hotels all over the world.