Complex sentence: In the "Bhagavad-gita" (9.13-9.14) Lord Krishna states that great souls worship and glorify him single-mindedly, but the practice of kirtan was popularized as a means to this end in the bhakti movement of the Moghul era.
Split into simpler sentences: In the "Bhagavad-gita" (9.13-9.14) Lord Krishna states that great souls worship and glorify him single-mindedly. The practice of kirtan was popularized as a means to this end in the devotional revival of the Moghul era.