Greek democracy was established because of the idea that a person shouldn't be too powerful and rule the lives of others. They were so ruthless at it that they would choose people to rule and then if they became too powerful and popular they would exile them or punish them or similar things. It was a kind of mob mentality that supported new and popular people. It was not very democratic however according to modern understanding of democracy because many were not allowed to vote at all, including slaves who existed as an entire social class.