Deepavali is really dedicated to Mahalakshmi...

Narakasura Vadha
Image courtesy: Wikipedia

While the Mahabharata gets most attention due to the events and politics leading up to the Pandava-Kaurava war, episodes involving Krishna, their impact and scale establish His role as the undoubted protagonist despite several claimants.

The 3-day Deepavali festival begins with Naraka Chaturdashi, the middle day being the most important day, and the last day being Bali Padyami. The significance accorded to these days have wide variation, but here are the common ones.

It is interesting to note that of the 3 Deepavali days, the most important is actually dedicated to Mahalakshmi.

• Naraka Chaturdashi is the day Narakasura (son of Hiranyaksha - Varaha avatara) was killed by Krishana. For the Narakasura Vadha, Satyabhama (an avatara of Lakshmi) accompanies Krishna and stays with him throughout the war. It was a war, for entire armies of Narakasura are vanquished by Krishna, and finally felled by his chakra.

• Bali Padyami is the day that Vishnu as Vaamana ends the asura king Bali's reign. This is probably the most peaceful episode you can find of an 'evil' king being vanquished. Bali offers Vaamana (in brahmin form) anything he might desire. He ends up committing three measures of land, measured by the tiny Vaamana's feet. After Vaamana grows and grows to cover earth and the skies, Bali keeps his commitment by offering his own head as the third measure. Vaamana blesses Bali, the grandson of Prahlada, but puts his reign to and end by pushing him to the nether world. It is important to note that while Bali himself was pious (though an asura), it was his fellow asuras that were out of control, which brings Bali his fate. A lesson to be learned here about turning a blind eye to wrong deeds.

These two major events, flanking the main Deepavali day, commemorate the elimination of two key villains that even Indra and the devas are unable to defend against. In both cases, boons granted to the two villains allow their day of exit to be celebrated.

Now to what I think is the main significant of Deepavali. 

Rukmani and Sathyabama, both contemporary avatars of Lakshmi, form actors in an episode that we can learn from. The episode is described well in this Wikipedia article (see Tulabharam section). In this episode catalyzed by Narada (he tries to kindle a rivalry between Sathyabama and Rukmani for Krishna's attention), Sathyabama depicts wealth (focusing on gold to match Krishna's weight in a tulabharam) whereas Rukmani finally matches Krishna's 'weight' by using a non-material-focused devoted offering of a tulasi leaf. 

I don't believe that Sathyabama was some material-focused princess who somehow ended up marrying Krishna. For, if Krishna is omnipotent, any of His consorts, in whatever yuga or avatara, can only be avataras of His eternal consort, Mahalakshmi. I strongly believe Lakshmi shows, through the Tulabharama episode, that the material-focused Sathyabama is not dearer to the Supreme being. It is the non-material focused, but devoted Rukmani.

This leads us to why Mahalakshmi might be the focus of Deepavali. It might be okay to treat Her as the goddess of wealth, which is not incorrect. However, the key reason to celebrate Mahalakshmi's role is for her lesson that devotion to God is more important than the pursuit of wealth. 

After the Mahapralaya, when creation has ceased, and everything is made dormant, Mahalakshmi is believed to plead with the Lord to wake from his yoganidra and restart creation for the benefit of the souls that may be awaiting their turn for saadhana and salvation. Because it is due to Her grace that souls, good and bad, get put into creation by the Supreme being, She is the mother of all. And that is why celebrating Her motherhood in this vein is the main significance of Deepavali.