He determined to discover the reason living beings suffer to solve the problem of suffering (dukkha).
He returned to his former family and country, to teach the Path to the end of suffering for all who seek freedom.
He established monastic communities of women and men of all castes that preserve and intensely practice the Teachings or "Dharma."
He was known by many titles including "the Buddha," the founder of the Buddha-Dharma ("Doctrine of Awakening") we today call Buddhism.
It invites humans and devas to "come and see," to test the validity of the Teachings by practice.
It is fully verifiable in the is very life. There is no need to wait until one dies to see if one had made a good choice or been practicing correctly. One can visit the many heavens, miserable planes, and Dharma realms while living as a tranquil, persistent meditator.
One sees for oneself the immediate (timeless) benefits of practicing the Dharma, abandoning the unwholesome and taking up profitable things.
So atheists and agnostics, polytheists, pantheists, and even theists can keep their beliefs and find support for them in the Teachings (with just a broader view to see how it is not crucial to believe one thing or another).
The truth to be found and realized for oneself goes beyond all limitations. Even the "divine" (devas, unseen beings, shining ones, nature spirits, messengers, celestials, extraterrestrials, beings of light) have something to realize.