I am NOT a scholar of Gauḍīya Vaiṣṇavism (03/27/14)
I’ll have to wait to return to my library in India to give you any details or an extensive answer, but in brief the Lord sends His associates well in advance of His own appearance and they leave bits and pieces of the nectar here and there for the Lord to relish. In most cases though, that highest truth descends in them and they are really not aware of it’s highest significance.
In the case of Mādhavendra Purī, it was Śrīmatī Rādhārāṇī who personally manifest Her bhāva thru him at the last moments of his life. Prior to that, he only had the association of māyāvādīs and Madhvas. It was Her causeless mercy.
Mādhurya-rasa did appear here and there prior to Mahāprabhu, so it is not actually that mādhurya-rasa was unknown. That is not the highest or the highest feature of Mahāprabhu. The highest features, hitherto unknown prior to Mahāprabhu were mahābhāva and vipralambha-sambhoga (union in separation). The seed was given by Mādhavendra Purī, but the plant was grown and the fruits harvested by Mahāprabhu.
Also mañjarī-bhāva, another of the top most realms in mādhurya-rasa, only became known thru Mahāprabhu and His associates. But all these things are mentioned (usually hidden) in Vedic literature. Usually they remain a mystery to those who are not in the paramparā, or who have not received causeless mercy. Śukadeva Gosvāmī is an example of causeless mercy.
There is much, much more to say in answer to your question – much too much for an email. These higher topics are better discussed in person.
And by the way…I am NOT a scholar of Gauḍīya Vaiṣṇavism, nor do I aspire to be. So don’t expect that I know everything. My only aspiration is to be accepted as a servant of my Divine Masters and my only qualification is their causeless mercy. That’s a fact.