Although Hiranyakasipu performed austerity for a long, long time, he was nonetheless known as a Daitya and Raksasa. Even great saintly persons could not perform such a severe type of austerity. Why then was he called a Raksasa and Daitya? It is because whatever he did was for his own sense gratification. His son Prahlada Maharaja was only five years old, and so what could Prahlada do? Yet simply by performing a little devotional service according to the instructions of Narada Muni, Prahlada became so dear to the Lord that the Lord came to save him, whereas Hiranyakasipu, in spite of all his austerities, was killed. This is the difference between devotional service and all other methods of perfection. One who performs severe austerities for sense gratification is fearful to the entire world. whereas a devotee who performs even a slight amount of devotional service is a friend to everyone (suhrdam sarva-bhutanam). Since the Lord is the well-wisher of every living entity and since a devotee assumes the qualities of the Lord, a devotee also acts for everyone’s good fortune by performing devotional service. Thus although Hiranyakasipu performed such a severe austerity, he remained a Daitya and a Raksasa, whereas Prahlada Maharaja, although born of the same Daitya father, became the most exalted devotee and was personally protected by the Supreme Lord. Bhakti is therefore called sarvopadhi-vinirmuktam, indicating that a devotee is freed from all material designations, and anyabhilasita-sunyam, situated in a transcendental position, free from all material desires.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 03 – Text 15 & 16