vyaktir bhagavato nṛpa
nṛṇām — for humanity; niḥśreyasa — of the highest benefit; arthāya — for the purpose; vyaktiḥ — the personal appearance; bhagavataḥ — of the Supreme Lord; nṛpa — O King; avyayasya — of Him who is inexhaustible; aprameyasya — immeasurable; nirguṇasya — untouched by material qualities; guṇa-ātmanaḥ — the controller of the material modes.
O King, the Supreme Lord is inexhaustible and immeasurable, and He is untouched by the material modes because He is their controller. His personal appearance in this world is meant for bestowing the highest benefit on humanity.
Since Lord Kṛṣṇa descends to benefit mankind in general, why would He neglect innocent young girls who loved Him more than anyone else did? Although the Lord awards Himself to His pure devotees, He is avyaya, inexhaustible, because He is aprameya, immeasurable. He is also nirguṇa, free of material qualities, and thus those who intimately associate with Him are on the same spiritual platform. He is guṇātmā, the controller or original personality behind the modes of nature, and it is specifically for this reason that He is free of them. In other words, because the modes of nature are His energy, they cannot act upon Him.