What does Gladwell mean when he states, "The outlier, in the end, is not an outlier at all" in Outliers: The Story of Success?

Gladwell begins the book with the definition of what an outlier is: a person who is seen as “markedly different” from everyone else, either in terms of extraordinary talent, success, or both. Throughout the narrative, Gladwell provides examples of these types of people, like computer entrepreneurs and Canadian hockey players. What he finds in his research, however, is that each one of these individuals had some kind of advantage beyond his or her control. These included historical timing, cultural differences, and even some beneficial nuances of language. It turns out their successes are not only explainable, but sometimes even predictable. This conclusion means outliers are NOT markedly different individuals after all. Gladwell says exactly this on the last page of the text:

They are products of history and community, or opportunity and legacy. Their success is not exceptional or mysterious. It is grounded in a web of advantages and inheritances, some deserved, some not, some earned, some just plain lucky – but all critical to making them who they are. The outlier, in the end, is not an outlier at all.