The Buddha's Buddhism was, so to speak, simply his realization of God, which in Japanese is called Satori. He had left his friends, his brothers, and his teachers Ramaputra and Kalama because their attitude was was to become one with Brahma in meditation, so that meditation became the main reason for surviving on earth.
The Buddha left them. He could not accept such a theory, and he went alone to sit under the Bodhi tree. All of a sudden---he realized: THIS is God, THIS is ALL! The endless sky is the extension of this body, and the earth, covered with mountains and divided by rivers, is also this very body---and trees, weeds, insects, flowers, and other human beings are also Buddha's body; and this soul is the soul of the universe, the soul of God.
He realized that prayer (and reasoning) are not necessary to prove God. All of a sudden
---"THIS is THAT." THIS is his standpoint.
--- from "The Zen Eye" by Sokei-an