In 1460 a Greek manuscript of the Corpus Hermeticum reached Florence. Cosimo de' Medici ordered Marsilio Ficino to set aside his translation of Plato and render it into Latin first, which he did in 1463. The priority is the point: the texts were believed to be the work of an Egyptian sage contemporary with, or older than, Moses, and therefore to preserve a primordial revelation, a prisca theologia, an ancient theology running from Hermes through Orpheus, Pythagoras and Plato, and agreeing in advance with Christianity.
On that basis Hermeticism became a central current of Renaissance thought. Ficino developed a natural magic of planetary correspondences; Pico della Mirandola joined it to Kabbalah; Giordano Bruno pushed it toward a radical cosmology and was burned in 1600, though his Hermeticism was one element among several in his condemnation. The literature fed alchemy, astrology, medicine, art and political theory, and the assumption of Egyptian antiquity was fundamental to its authority.
That assumption was destroyed in 1614, when the philologist Isaac Casaubon examined the Greek of the Corpus Hermeticum and showed that it could not be ancient. The vocabulary is late, the philosophical terminology belongs to the Hellenistic schools, the texts are written in prose of the Roman imperial period, and they refer to matters postdating any conceivable Egyptian sage. His dating, roughly the first centuries CE, has been confirmed by everything found since and is not seriously disputed.
The effect on scholarship was immediate and the effect on practice was slight. Hermetic material continued to circulate through the Rosicrucian manifestos, through alchemy and Freemasonry, through the eighteenth and nineteenth centuries, and into the Hermetic Order of the Golden Dawn, founded in 1888, which put the name on the movement from which most modern Western ceremonial magic descends. The Kybalion, published anonymously in 1908 and widely sold as Hermetic philosophy, is a work of American New Thought with no ancient content whatever, and is frequently mistaken for the real thing.
Modern scholarship has also complicated Casaubon's verdict in one respect. A late date does not preclude Egyptian content, and specialists now identify genuine Egyptian religious material inside these Greek texts. The Hermetica are not pharaonic wisdom, but neither are they simply Greek philosophy in Egyptian costume.