In the scriptures it is written:
eka mahaprabhu, ara prabhu dui-jana
dui prabhu seve mahaprabhura charana
There is one ‘Mahaprabhu’. He is the famous Sri Gaurangasundar of Sri Nabadwip Dham, who later became known as Sri Krishna Chaitanya. Advaita Prabhu and Nityananda Prabhu, both are ‘Prabhu’ (Master), but Mahaprabhu is ‘Maha-Prabhu’ (the Supreme Master). Both Advaita Acharya and Nityananda Prabhu very happily served Mahaprabhu and spread His conception of Krishna consciousness throughout the universe during Their divine Pastimes. Advaita Prabhu prayed constantly with tears, Ganges water, and tulasi leaves for Lord Krishna to appear and rescue the fallen souls of Kali-yuga, and Mahaprabhu appeared in answer to His prayer. So Mahaprabhu appeared by the grace of Advaita Prabhu. But before Mahaprabhu appeared, Nityananda Prabhu also appeared and made all the arrangements for rescuing the souls of this world.