Navadvipa dhama is unique because it is audharya-dhama. There are terms that indicate the specialty of the Personality of Godhead. His opulence, aisvarya, is manifest in Vaikuntha. In Vrndavana, His madhurya, which is the mood of intimacy of love, is so strong that it eclipses the opulence and prevails. Although Krsna lifts Govardhana Hill and displays so many pastimes that show His omnipotence, the residents of Vrndavana overlook that because of the intimacy of their love. In Navadvipa, eclipsing even that mood of intimacy of love is audharya - the munificence, magnanimity, or compassion exhibited by Caitanya Mahaprabhu.
That is the reason for His appearance - to deliver love of God. Namo maha-vadanyaya krsna-prema-pradaya te. Freely! He just gives love of God. One may think, “I am not qualified.” Lord Caitanya's mood is, “Doesn't matter, take it anyway!” But, “I have got so many other interests.” Still, “Take it anyway!” He says.
The reason for Lord Caitanya's appearance is to give not only love of God, but love within the same mood as found in the love that the residents of Vrndavana feel for Krsna. That is what Lord Caitanya wants to give!
Adapted from a lecture by HH Romapada Swami entitled 'Lecture at Yogapitha - Entering the Dhama and Mahaprabhus Childhood Pastimes, Day 1, Mayapur Yatra November 2012 ' delivered in Mayapur.