FIRST of all he came into the world with a tremendous endowment; some people are simply born with unusual gifts.
SECOND Leaving school on the first day his mind was never subjected to the indoctrination most of us got from our teachers. "The primary object of primary education is to socialize the pupil to the conventions of the culture we belong to." That never happened to Blake. Instead he ....
THIRD read! and read! and read! He read the things that had fallen out of the national consciousness-- dominated by an extremely materialistic culture: the Bible, Behmen (Boehme) and hundreds of others, each in his own way representing the Perennial Philosophy. And he saw the Great Painters, not those favored by the Establishment.
FOURTH The population didn't read anything beyond the fourth grade level. When Paine asked Blake if people read him, he replied, "before the people can read it, they have to be able to read" (very much like today!). So there was a chasm between his mind and theirs (and ours).
The aforementioned video shows Tom Paine represented as the soul of rationality and Bill Blake the feeling, and above all the imagination.
So Blake's relationships were with God: Meister Eckhart, Mohammed, Isaiah, Ezekiel, Boehme, Jesus, other men who had had similar visions. He honored God with the "severe contentions of friendship & the burning fire of thought." (Jerusalem 91:17; E251)
His faith came up the hard way: Molech, Elohim, Nobodaddy, Urizen, and finally the Dear Saviour. How many of us good people can say we came to our faith like that?
Thank God we have the benefit of Blake's experience.