What was the cause of Krishna's death?

Interpretations of Krishna-lila: Kamsa

Kamsa represents the material consciousness and the materialist who takes all possible precautions and does not even shrink from atrocities in order to prevent Krishna consciousness or the appearance of Krishna. The sinful kamsa is the fear of Krishna in person and he always ponders how to kill his enemy. In spite of all his power and all his demonic assistants, however, he is destined to ultimately be dragged from his throne by Krishna and to find his deserved end as a punishment for his many wrongdoings.

Srila Bhaktisiddhanta Sarasvati Thakura describes King Kamsa in a well-known article (The Harmonist, Vol. XXIX, No. 7, 1932) as the typical aggressive, empirical philosopher who is always on the lookout for the appearance of the supernatural (Krishna) in order to then watch it suppress. Kamsa only believes in what he can see and understand, and because of this he feels an aversion to the supernatural, which he regards as dogmatism and hypocrisy under the guise of religion. If he were to fight the emergence of belief in the supernatural early enough, then he would be able to destroy it, he thinks. As an atheist, he regards the appearance and belief or devotion to the supernatural as heresy and superstition. In reality, however, he has no power over Krishna and wherever real Krishna consciousness appears, sooner or later this means the ultimate end of material consciousness.

Excerpt from the Srimad Bhagavatam:

Karmsa thought: What is my duty now? The Supreme Lord, who knows His purpose [paritranaya sadhunam vinasaya ca duskrtam], will not lose His strength. Devaki is a woman; she is my sister, and moreover, she is now pregnant. If I kill them, I will certainly lose my reputation and wealth, and my lifespan will be shortened. (02/10/21)

Sukadeva Gosvami said: This is how Kamsa reflected, and although he was determined to maintain his hostile attitude towards the Supreme Personality of Godhead, he refrained from the shameful murder of his sister. He decided to wait until the Lord was born and then do whatever was necessary. (02/10/23)

On his throne, in his living room, on the bed, practically everywhere he stayed, and while eating, sleeping and walking, Kamsa only saw his enemy, the Supreme Lord, Hrsikesa. In other words, by thinking of his all-pervading enemy, Kamsa became Krishna conscious in a negative sense. (02/10/24)

A nondevotee or atheist also develops God-consciousness by trying to avoid God at all costs. For example, the so-called scientists who want to create life with the help of chemical manipulations consider the external, material elements to be the highest. The idea that life is part of the Supreme Lord is against such scientists. As clearly stated in the Bhagavad-gita (mamaivamso jiva-loke jiva-bhutah), living beings do not arise from a combination of material elements (earth, water, fire, air and ether), but are separate components of the Supreme Personality of Godhead. If one understands the position of the living being as a separate part of the Supreme Personality of Godhead, then by studying the nature of the living being one can understand the nature of the Supreme Lord, for the living being is a tiny image of God. But because atheists want nothing to do with God consciousness, they try to become happy by developing Krishna consciousness in various negative forms.
Although Kamsa was always lost in thought of Hari, the Supreme Personality of Godhead, he was not happy. A devotee, on the other hand, is always happy, whether he is sitting on a throne or under a tree. Srila Rupa Gosvami resigned from his post as government minister to sit under a tree, but he was happy nonetheless. Tyaktva turnam asesa-mandalapati-srenim sada tucchavat (Sad-gosvamy-astaka 4). He did not value a peaceful life as a minister, but was even happy under a tree in Vrndavana, as he served the Supreme Personality of Godhead in a benevolent attitude. This is the difference between a devotee and a nondevotee. For a nondevotee the world is full of problems, while for a devotee the whole world is full of bliss. (Bhaktivedanta commentary on 10.2.24)

Excerpt from "Krishna - The Supreme Personality of Godhead", Kamsa's death, chapter 43

All the people gathered in the wrestling arena applauded enthusiastically. Their joy knew no bounds and those present brahmanas began to praise Krishna ecstatically. Only Kamsa was cross. He neither clapped his hands nor gave his blessing to Krishna. He was annoyed that the drums were being struck in honor of Krishna, and he was very sorry that his wrestlers were either dead or had fled the arena. So he stopped the drumming and said to his friends: "I order that the two sons of Vasudeva are chased out of Mathura immediately. The cowherd boys who have come with you are to be plundered and robbed of all riches. Nanda Maharaja takes for his immediately Cunning and killing him, and killing the villain Vasudeva without delay. My father, who constantly supports my enemies behind my back, should also be eliminated. "
When Kamsa said this, Krishna became very angry and in seconds jumped over the great bodyguards who surrounded King Kamsa. Kamsa was prepared for Krishna's attack, because he knew from the beginning that this would be the cause of his death, and so he immediately drew his sword and prepared to face Krishna's attack with weapon and shield. But although Kamsa was lashing out with his sword, Sri Krishna, the most powerful lord, grabbed him with great strength. The Supreme Personality of Godhead, who is the refuge of all creation, and from whose lotus navel creation emerges, immediately knocked the crown off Kamsa's head, reached into his long hair and pulled the king down from the throne to the battlefield, where He laid him on the ground threw. Krishna quickly sat astride the demonic king's chest and hit him again and again with his bare fist. With these punches, Kamsa lost all life force.
In order to show his parents that Kamsa was really dead, Krishna dragged him through the arena like a lion dragging away a killed elephant. At this sight there was a roar through the crowd, as some of those present cheered loudly while others broke out in loud wailing. From the day Kamsa learned that he was going to be killed by Devaki's eighth son, he had thought of Krishna for twenty-four hours a day without a break - when he ate, when he walked, and with every breath - and therefore he would he was naturally blessed with deliverance. The Bhagavad-gita explains: sada tad bhava bhavitah (BG 8.6) - according to the thoughts with which one is constantly occupied, one receives the next body. Kamsa now thought of Krishna in the form in which He carries a wheel of fire, that is to say of Narayana, who is holding a wheel of fire, a conch shell, a lotus flower and a club in His four hands.