A tree has no consciousness: when cut, it feels no pain. But Nārada Muni wanted the consciousness of Nalakūvara and Maṇigrīva to continue, so that even after being released from the life of trees, they would not forget the circumstances under which they had been punished. Therefore, to bestow upon them special favor, Nārada Muni arranged things in such a way that after being released, they would be able to see Kṛṣṇa in Vṛndāvana and thus revive their dormant bhakti.
Each day of the demigods in the upper planetary system equals six months of our measurement. Although the demigods in the upper planetary system are attached to material enjoyment, they are all devotees, and therefore they are called demigods. There are two kinds of persons, namely the devas and the asuras. Asuras forget their relationship with Kṛṣṇa (āsuraṁ bhāvam āśritāḥ), whereas the devas do not forget.
- dvau bhūta-sargau loke 'smin
- daiva āsura eva ca
- viṣṇu-bhaktaḥ smṛto daiva
- āsuras tad-viparyayaḥ
- (Padma Purāṇa)
The distinction between a pure devotee and a karma-miśra devotee is this: a pure devotee does not desire anything for material enjoyment, whereas a mixed devotee becomes a devotee to become a first-class enjoyer of this material world. One who is in direct touch with the Supreme Personality of Godhead in devotional service remains pure, uncontaminated by material desires (anyābhilāṣitā-śūnyaṁ jñāna-karmādy-anāvṛtam [Bhakti-rasāmṛta-sindhu 1.1.11]).
By karma-miśra-bhakti one is elevated to the celestial kingdom, by jñāna-miśra-bhakti one is able to merge in the Brahman effulgence, and by yoga-miśra-bhakti one is able to realize the omnipotency of the Supreme Personality of Godhead. But pure bhakti does not depend on karma, jñāna or yoga, for it simply consists of loving affairs. The liberation of the bhakta, therefore, which is called not just mukti but vimukti, surpasses the five other kinds of liberation-sāyujya, sārūpya, sālokya, sārṣṭi and sāmīpya. A pure devotee always engages in pure service (ānukūlyena kṛṣṇānuśīlanaṁ bhaktir uttamā (CC Madhya 19.167)). Taking birth in the upper planetary system as a demigod is a chance to become a further purified devotee and go back home, back to Godhead. Nārada Muni indirectly gave Maṇigrīva and Nalakūvara the greatest opportunity by his so-called curse.