Why were the Olympic Games the symbol of peace and friendship?

The Olympic Games have a very long history. They began in 777 BC in Greece and took place every four years for nearly twelve centuries at Olimpia. They included many different kinds of sports: running, boxing, wrestling, etc. All the cities in Greece sent their best athletes to Olimpia to compete in the Games. For the period of the Games all the wars stopped. So the Olympic Games became the symbol of peace and friendship. 
In 394 AD the Games were abolished and were not renewed until many centuries later. 
In 1894, a Frenchman, Baron Pierre de Coubertin, addressed all the sports governing bodies and pointed out the significance of sports and its educational value. 
Two years later the first modern Olympic Games took place. Of course, the competitions were held in Greece to symbolize the continuation of the centuries-old tradition.