Why did Gilgamesh, which had been widely known, vanish for so long?

Gilgamesh was an epic tale widely known and narrated throughout ancient history. Unfortunately, the it was written about disappeared, as did their culture.......... the legend lasted for as long as the stories were kept alive with oral tradition. Discoveries (partial) of tablets re-awakened interest in the story, but incomplete versions were the result. The epic now available is a product of thousands of years of development........ but it is fantastic.