PURPORT

Devaki, the mother of Krishna and sister of King Kansa, was put into prison along with her husband Vasudeva because the envious king was afraid of being killed by the 8th son (Krishna) of Devaki. He, therefore, killed all the sons of Devaki who were born before Krishna but Krishna escaped the danger of childslaughter by his maternal uncle because He was transferred to the house of Nanda Maharaj Lord Krishna's foster father. Kunti Devi was also saved from a series of dangers along with her children. But Kunti Devi was shown more favor because Lord Krishna did not save the other children of Devaki while He saved the children of Kunti Devi. This was done because Devaki's husband Vasudeva was there living but Kunti Devi was a widow and there was none to help her except Krishna. The conclusion is Krishna endows more favor to a devotee who is in greater dangers of helplessness. Sometimes He puts His pure devotees in such dangers because in that condition of helplessness the devotee becomes more attached to the Lord. The more the attachment is there for the Lord the more success is there for the devotee.