The Fertile Crescent is a crescent-shape region in the Middle East. It is an area watered by the Tigris, Euphrates, Nile and Jordan rivers. It has been an area rich in human activity as well as agriculture and today is home to about a quarter of the Middle East's population.
Reliable flooding of the Nile River allowed for dependable crop production.
I believe it's because it was one of the earliest, if not the earliest areas in which societies sprang up and became prevalent