In the era, that Krishna was born, and before, people worshiped god in the form of Indira, Agni, Varuna, Vayuu, etc. The nature, its forces and fury were paid full obeisance. The original forms of god, were these. Slowly but steadily, they were replaced by other forms of beings for worship. Like all other living beings, and life on this earth, it appears religion too evolved along with the human social upliftment and civilizations.
Krishna, was not the first of the reformer, or the creator of a new paradigm for our religion, nor was he the last. But even after many thousand years, he seems to have caught the fascination of people. People seem to be able to bond with Krishna at all levels, in all forms and through different means. The puranas and bhagavatham are filled with stories of how Krishna changed or challenged thoughts of the time he lived in. Constantly explaining and reintrepreting religion as we knew it then. Constantly reminding his followers, he is god, and none other.
One story about Krishna attempts at reform, centers around the Govardhan hill. Krishna came up on his tribe and villager, preparing for rituals and tributes to be offered to Indira, at the end of the monsoon season. He disauaded the villagers from offering prayers to Indira, the rain god. He explained that it is foolish to pray to someone sitting in the heaven, and someone who is supposedly responsible for all the good harvest. Instead, prayers should be offered to Govardhana, the hill right in front, that nutures live and provides the people and animals with all their needs. The story goes on to illustrate how Krishna taught Indira a lesson. How he protected the people by lifting the Govardhan hill, with his little finger.
If you choose to believe these theatrics, then you still come to understand that Krishna is the god almighty. If you dont, you then can gleam just the philoshpical truth behind the story, and still come to the same conclusion. There in, lies the essence of religion, specially the story of Krishna. As a child you can revel in the naughtiness and the playfullness of the baby. As a youth, you learn about love, like it shown or taught anywhere else. As you grow older, then you can reflect on the same stories, and see the more plainer truth and the real meaning of god, prayer and religion.