Who invented entertainment?
I may be wrong, but I think entertainment was invented by the Romans, as an alternative to violent entertainment.
Classical Theatre was created by the Greeks although it naturally rises out of storytelling in other parts of the world.
Greek Theatre originated as part of religious festivals though the year. As part of these events, story telling and then acted out storytelling were part of the religious experience. Originally there were no more than 2 actors on the stage at one time. One would leave and another would enter as the story developed. The stories had a moral at the end.
A chorus was added to help re-enforce and narrate the story. The Chorus would often speak the moral at the end of the play.
Theatre is the study of life. Religion to provide purpose and order to living. In this way the Greek Theatre was a religious experience.
The Greeks wrote down a lot a basic aesthetics. Aristotle's "Poetics" was one. These have managed to survive the millennia and are still of use today. Many Greek plays are still performed to appreciative audiences.