Prahlada Maharaja was the son of the most atheistic and the most materially powerful person - Hiranyakashipu. Because the society was materialistic, he had no opportunity to glorify the Supreme Lord.
The characteristic of a great soul is that he is very eager to broadcast glorification of the Supreme Lord. Lord Jesus Christ, for example, was very eager to broadcast the glorification of God, but demoniac people misunderstood him and crucified him.
Prahlada Maharaja requested his friends, who were all sons of demons, to give up the idea that there is no God and convinced them to engage in the loving service of Lord Krishna.