Either you kill the power or you kill the powerful – the result is the same. Krishna is the intelligence of the intelligent, he gave some home truths to Lord Indra and said ” No living entity can independently become opulent; one must be favored by my mercy, you should always remember that all your opulence’s are due to my mercy”. So Krishna reminded him of his duties.
One of the main reason Krishna did not kill kaliya is, Kaliya in his past birth was the sage” Vedshira” who had performed severe austerities. The rishi Vedshira lived in a beautiful ashram and once the “Ashvashira” muni entered in his ashram, seeing him coming, the sage Vedshira shouted on him and said” You are not supposed to perform any penance here, just get out of this place”. Seeing envious and full of hatred behavior ashvashira muni cursed him and said” You are behaving like a serpent who is always angry and envious to others, therefore I curse you to become a snake”. Now, any man blessed with such an instincts will surely become a poisonous snake in his next life.
When Krishna was subduing Kaliya, Kaliya’s wives said” One cannot come in contact with Krishna without having executed pious activities in devotional service in his previous lives”. So, all those are worshipping Krishna must have performed great austerities in their previous lives. Kaliya was fortunate to have realistic and mature wives. The Nagpatnis instead of cursing Krishna said” The punishment which you have so kindly offered is exactly befitting and that is your purpose to annihilate the disturb elements within this world”, so we think it is benediction and your mercy upon us, as even when you punish, the sins are eradicated”. Kaliya’s wives knew that our job is to please Krishna-not to be against him.
In another case, wife would have filed divorce case against the villain husband like this. The kaliya daman is also an instruction to the offender of Vaishnavas. Any man who commits a serious offense against vaishnav, falls down from his position. Garuda the carrier of Lord Vishnu would come to Yamuna River to catch and eat fish, this didn’t go down well with Saubhari muni that lived there and he was deeply attached to the fish. Saubhari muni cursed Garuda saying” Henceforward, from this day, if Garuda comes here- he will be immediately killed”. The snakes are always fearful of Garuda as Garuda eats them and Garuda had beaten Kaliya in the past. Kaliya knew this curse and therefore, he started living in Yamuna.
Subduing Kaliya is a hidden glorification of Garuda who is always in the association of Lord Vishnu. Saubhari muni was not saved from this offense against a vaishnava, he fell down from his yogic position and afterwards became a householder- a sense enjoyer in the material world. The sage Vedshira and Saubhari muni were exalted devotees once upon a time but their one mistake brought about their downfall, it means, devotees have to be careful while performing devotional service to Krishna. A devotee cannot afford to commit vaishanav Apradh.
Krishna was the real nature lover, Instead of worshipping Indra he told Brajvasis to worship Goverdhan, The prince of mountain Goverdhan pleased Krishna with his service, mountain plays vital role in maintaining the balance of nature, Krishna knew it and therefore he gave importance to Goverdhan who assisted Krishna in his lilas. Similarly Krishna gave importance to the purification and cleaning of River Yamuna. When Krishna came to know that kaliya’s poison is contaminating Yamuna he decided to clean it. Krishna is the number one purifier, after subduing and purifying kaliya he purified Yamuna water. The Yamuna’s water was so poisonous that the cows and the birds would die after drinking it. Therefore to save the brajvasis, to save the Yamuna, to save the animals he sent kaliya to Raman dwip. This is what Krishna does when he is forced to such situations, we have been given the same situation, all the rivers in India are getting contaminated and aquatic animals in it are dying slowly. Only Krishna can save them.
The Kaliya subduing story gives another lesson of how one should be attached to Krishna. When the Brajvasis came to know that Krishna is enveloped in the coils of serpent they were stunned out of fear and fell down. Even the cows, bulls and small calves became overwhelmed with grief and started crying. All the Brajvasis including animals were just on the point of death as they had dedicated everything to Krishna: their lives, property, affection, activities everything was for Krishna. Then Lord immediately captured the hoods of Kaliya and started kicking and dancing on it.
As if Krishna wanted to entertain the grief stricken Brajvasis but Krishna did not kill kaliya he killed the envy, hatred and anger inside him.