Education, History, and Winners

Postmodernists reject the study of history because it is a "winner's narrative." My question is, why wouldn't you want to study history based on what has succeeded? Why study failure? Why study the viewpoint of those who have failed? 2,500 years ago, when there was substantially less history (and more failure), Sun Tzu said that only way to learn how to be successful was to study the history of success. What does it say about a civilization that doesn't understand the importance of that concept? Is it headed for more success or something else?