This session's topic: Early Greek ReligionThe early peoples that inhabited the land that we now know as Greece did not always worship Zeus or the other Olympians that we now know of today. They were very agriculture-based (agrarian) societies, and much of their religions were based on fertility, and in turn, goddess-worship. I wasn't until later times, around the time of the Trojan War, that the male gods became more important that the female goddesses. Being very dependent on the fertility of their crops to survive, the people turned to those who gave birth to new life: the women.
Dionysus was a very important god to those early people. He represented rebirth and fertility, and was not the almost petty god of wine as we see him today. At the end of each season he would "die", and his remains would be sewn back into the earth (the goddess figure) so that he could be "reborn" in the spring with the plants from the womb of the goddess. If he was not redelivered into the earth, it could not become fruitful again, and no plants could grow. This is where the model Greek theater came from: The protagonist (the hero) suffers a great defeat and over comes it to be reborn stronger and wiser than he was before.
If you are interested in reading about these topics, I highly recommend Mary Renault's Novel The King Must Die, and Sophocles' play, "Oedipus Rex".