why is Diwali celebrated?

Diwali, the festival of lights, is the major Hindu Festival celebrated in India and Millions of Indian abroad. Why this festival is celebrated by this much number of people?

The Hindu Diwali is comparable to Christians Christmas somehow, but not exactly. The birth of Jesus is celebrated as Christmas, whereas the death of Demon king 'Naragasura' is celebrated as Diwali.

Demon king naragasuara was the cruel person who killed the Good Rishis, Devas and other people. The prominent hindu God MahaVishnu Killed Naragasura in the war with the Demon King. This is day celbrated every year by exchanging wishes and sweets, wearing new clothes and fire crackers.