Until someone with more knowledge than me answer:

It's the french Pierre de Coubertin who founded the current Olympic committee (that's why the official language is French and there is always an announcer speaking french in the beginning of events). But he wasnt the first one attempting to revive the games. He was inspired by Greek Olympic games founded by Evangelos Zappas. the first Olympic game was held in Athene in 1859 with athlete from Greece and the ottoman empire. Pierre de coubertin saw the Olympian game of 1890 and founded theinternational committee and making the Olympic game a world wide event.

One of his motivation was his interest in sport. he believe sport should be patriced by men, interesting quote from wikipedia :

As a historian and a thinker on education, Coubertin romanticised ancient Greece. Thus, when he began to develop his theory of physical education, he naturally looked to the example set by the Athenian idea of the gymnasium, a training facility that simultaneously encouraged physical and intellectual development.

and

|...] his advocacy for physical education was based on practical concerns as well. He believed that men who received physical education would be better prepared to fight in wars, and better able to win conflicts like the Franco-Prussian War, in which France had been humiliated.

and

Additionally, he also saw sport as democratic, in that sports competition crossed class lines, although it did so without causing a mingling of classes, which he did not support.

it's kinda a mix between national pride and the desire to make his fellow countrymen better.