Why did the age of expansion happen?

Greece's Dark Age Ended Around 800-750 B.C. (BC Means Before Christ) Cities Grew Trades Increased People In Neighboring Cities Got Together And Traded With One Another Leaders Arose Among The People in Each City Until Each City Became A Separate Small Country Or State The Cities Were Called City States Some City States Became So Big They Needed More Farmland To Support More People This Lead To Fights For Land Some Greeks Left Their Current City State To Find New Ones Greek City States Flourished In The 600 And 500 B.C. A Period Known As The Age Of Expansion