Alphonse-Louis Constant trained for the Catholic priesthood and got as far as deacon before leaving in 1836. He spent the next fifteen years as a radical journalist and pamphleteer, was imprisoned more than once for his politics, and only in the 1850s reinvented himself as Eliphas Levi Zahed, a Hebraized form of his own two names. The magician was a second career built on the wreckage of a first.
This matters for reading him. Levi did not inherit a tradition; he assembled one. Christopher McIntosh's study traces the components, Catholic sacramental theology, Swedenborg, Mesmer's magnetic fluid, Fabre d'Olivet, Court de Gebelin's tarot speculations, and the Kabbalah he read in Christian translation rather than in Hebrew. What he added was the organising nerve to put them into one system and write it in prose that people wanted to read.
Two of his inventions became so standard that they are now mistaken for ancient doctrine. The first is the Astral Light, a universal plastic medium that transmits magical effect, a Mesmerist fluid given a cosmological job. The second is the correspondence of the twenty-two tarot trumps to the twenty-two letters of the Hebrew alphabet. That pairing is not medieval, not Egyptian and not Jewish; Decker and Dummett date it to Levi and his immediate French predecessors. Nearly every esoteric tarot system since, including the Golden Dawn's, is a variation on his scheme or a deliberate rearrangement of it.