How did democracy and other forms of government develop in Greece?

it started in 5th Century BCE by Cleisthenes

Explanation:

Cleisthenes Introduced the concept of demokratia. Which can be translated as "People power". It's a concept that he developed as an alternative from a monarchy system which often put one king in an absolute position of power. Many of them ended up becoming tryannical and supress his own people.

To create a fairer society, he proposed a new concept of government, where the people were involved in the creation of laws and government program.

He elected a group of people with a lottery (purely based on luck) in order to act as "jurors", which is basically the representative of the people. The jurors can directly cast out their vote to determine which type of legislations should be created in their community.