Jamaica is a country that used to have one male and one female sprinter that was consistently in contention for an Olympic medal, with a solid relay team that also had the ability to compete for a medal sometimes.
In the last 10-12 years that has all changed. Jamaica has won the last 2, 4 x 100 Men's relay Olympic Gold Medals. Prior to that, Jamaica had only medaled once in the 4 x 100 Men's relay, a silver back in 1984.
Jamaica is a country of approximately 3 million people. That is like the state of Mississippi suddenly becoming a dominate power in sprinting almost over night.