The vine of devotion, which Śrīman Mahāprabhu gave to the people of the world, yields the fruit of brilliant rasa, the amorous love of Vraja, particularly the rasa of the most confidential personal service of Śrīmatī Rādhārānī, named mañjarī-bhāva-sādhanā.

This great gift was not given before by any other descension of God; even the wise men who were experts in devotion to God did not know this secret fruit of the vine of devotion. They used to practice vaidhi-bhakti, regulated devotion to God, out of fear and respect for the Supreme Lord, and even if there were any rāga-bhaktas in the Vraja-bhāva before Mahāprabhu’s descension, they all would be serving Kṛṣṇa in the mood of a servant or a friend. Nobody knew the secret of the sweet devotional love of the gopīs for Kṛṣṇa, what to speak of the topmost mādana-mahā-bhāva of Śrī Rādhā, the crown jewel of all the gopīs!
The wish-yielding vine of devotion revealed by Mahāprabhu was also hidden in the Vedas.

In the pre-Caitanya era there was a cult of sakhī-bhāva (love for Kṛṣṇa as a participating amorous consort) preached by great devotees like the poet Jayadeva, Caṇḍīdāsa, Vidyāpati, Bilvamaṅgala and others, but the mañjarī-bhāva-sādhanā, the personal and exclusive service of Śrī Rādhā, was a new gift, introduced by Śrī Gaurasundara and the ācāryas who took shelter of His lotus feet.
The seed of this vine of devotion is given by a Gauḍīya Vaiṣṇava saint or guru and it is sprinkled by the water of hearing, chanting and remembering, so that the vine will ultimately bear the ripened, delicious fruits of rādhā-dāsya-bhāva.

One may ask now: “Why did Śrīman Mahāprabhu reveal this confidential bhakti-kalpalatā, which is not perceived even by the great sages or the Vedas, to the degraded and sinful people of the present age of Kali (quarrel)?
The plain reason is that Śrīman Mahāprabhu is the fully independent and most merciful descension of God, therefore it is said here: kṛpālus tāṁ gauḍe prabhur ati kṛpābhiḥ prakaṭayan.
“The completely independent and capable Śrīman Mahāprabhu has most mercifully revealed this in Bengal.”
The mercy of the Lord completely erases the candidate’s unworthiness. The kṛpā-sakti (power of compassion) is the crown jewel of all the Lord’s innate potencies and makes Him truly worthy of the title Bhagavān, the Qualified One.

Srila Ananta das Babaji