balarāma ha-ila nitāi
dīna-hīna yata chila, hari-nāme uddhārila,
ta’ra sākṣī jagāi-mādhāi
The appearance of Śrī Caitanya Mahāprabhu in this Kali-yuga is especially meant to deliver the fallen souls, who are always planning something for material enjoyment. He gave the people of this age the advantage of being able to chant the Hare Kṛṣṇa mantra and thus become fully pure, free from all material contamination. Once one becomes a pure Vaiṣṇava, he transcends all material conceptions of life. Thus Kaśyapa Muni tried to transform his wife into a Vaiṣṇavī so that she might give up the idea of killing Indra. He wanted both her and her sons to be purified so that they would be fit to become pure Vaiṣṇavas. Of course, sometimes a practitioner deviates from the Vaiṣṇava principles, and there is a chance that he may fall down, but Kaśyapa Muni thought that even if one falls while practicing the Vaiṣṇava principles, he is still not a loser. Even a fallen Vaiṣṇava is eligible for better results, as confirmed in Bhagavad-gītā. Svalpam apy asya dharmasya trāyate mahato bhayāt: even practicing the Vaiṣṇava principles to a small extent can save one from the greatest danger of material existence. Thus Kaśyapa Muni planned to instruct his wife Diti to become a Vaiṣṇava because he wanted to save the life of Indra.