Several groups fought over control of the sanctuary at Olympia, and hence the games, for prestige and political advantage. Pausanias later writes that in 668 BC, Pheidon of Argos was commissioned by the town of Pisa to capture the sanctuary from the town of Elis, which he did and then personally controlled the games for that year. The next year, Elis regained control.
In the first 200 years of the games’ existence, they only had regional religious importance. Only Greeks in proximity to the Olympia competed in these early games. This is evidenced by the dominance of Peloponnesian athletes in the victors’ rolls.
The Olympic Games were part of the Panhellenic Games, four separate games held at two- or four-year intervals, but arranged so that there was at least one set of games every year. The Olympic Games were more important and more prestigious than the Pythian, Nemean, and Isthmian Games.
Source: Wikipedia