Broken down simply, Krsna(as Maha-Visnu) is the creator of the universe and all things in it, He created Brahma, who was the first devotee. That's how I learned it anyways.
Sri Brahma-samhita 5.18: When Visnu lying in the ocean of milk wills to create this universe, a golden lotus springs from His navel-pit. The golden lotus with its stem is the abode of Brahma representing Brahmaloka or Satyaloka