Scholars know that the olympics festival began early in Greek history because

because this is based on scripts that have been found in Olympia.

Explanation:

Sports competitions in honor of the gods were held earlier, and the Olympics, though most important, were not the only periodic games. Among the most famous were the games in honor of the goddess Hera, which also took place in Olympia, two years after each Olympiad. During that 776 BC The Olympics involved only one competition - a leg race or a stadium, between 180 and 240 meters long, lasting only one day. The origins of the Olympics are described by the ancient Greeks in several legends. They were held every four years, which in ancient Greece became a unit of time. Thus, in some writings records such as "the third year of the eighth Olympiad" or "the first year of the ninth Olympiad" can be found. The home of the competition, Olympia, belonged to the Greek city-state of Elijah on the Peloponnese, although neighbor Pisa had conquered this territory on several occasions for a short period.