Buddha's enlightenment! 2500 years ago, under the Bodhi tree in Magadha, what did Buddha realize?

What did Buddha Shakyamuni realize under the Bodhi tree in Magadha 2,500 years ago? It acknowledged the connection of why He got enlightened then. Why was Buddha Shakyamuni able to attain enlightenment? It was 'Kyokhu-kai' that place, and he recognized what the vacuum that has nothing was.
He realized that he was, in fact, in the 'Kyokhu-kai,' he was given 'Juki' by Tathagata Dipankara (Burning lamp Buddha). He told Buddha Shakyamuni to become Tathagata and preach the Lotus Sutra in the world he would be. When the Buddha Shakyamuni attained enlightenment, he found the system in the vacuum of nothingness. He found himself as 'Kyokhu-kai.' A vacuum of nothingness is 'Kyokhu-kai,' that is the system Tathagata tells Tathagata.
Buddha shakyamuni found the mechanism, the cause, of why he became enlightened.