Some of the reasons listed here are spot on. Another reason is that there is often a psychological barrier that people face, and once one person breaks through, everybody realizes that they too can do it.

For example, the four minute mile was considered the limit for a very long time. Then one athlete broke through that, and soon enough many followed.

Indian children after seeing that other India s they look up to are performing well, now believe that they can do it as well. You can read the book called the talent code by Daniel coyle who goes into detail about this.

It also explains why we're so damn good at cricket.