Scans_Daily

While you certainly have a pretty good grasp on the evolution of the fictional magician, I can help you with a few points about their real-world counterparts...

Merlin as a representative of Pre-Christian Britain is not a modern invention. Merlin shows up in Welsh stories going back to before the Arthurian myths. In Geoffery of Monmouth's depiction he's already got strong pagan influences.

Most of the Alchemists of middle ages and renaissance were mystics much moreso than scientists. Their writings (some of them) are still extant today, and it's clear that they believed that all the elements of the natural world had their reflection in God and therefore, because man was a reflection of God, were reflected in turn in the soul. So, the physical alchemy was primarily about the perfection of self, and the discoveries they made through these experiments led to incidental scientific realizations. Later, when you get to Enlightenment era alchemists, then you start to have some more genuine scientists working on the base of their mystical predecessors. Although you're right about Newton.

The old woman witches living on the outskirts of town were not a leap of logic, or a matter of scapegoating the mentally unstable. They were an actual thing. Going back to Pre-Christian Europe, medicine women (or cunning women) often lived on the outskirts of town, and were paid for services of healing, prophecy, blessings, and the lifting of curses (also the laying of curses, but you didn't talk about that). When the Christians came in the cunning women were largely left to do their business (at least at first), not because they approved, but because she was kind of a pillar of the community, and towns would fall apart without her. Hell, the priests would even send sick people to them. However, the first famine or plague to come along would inevitably be blamed on her. Hence, her fictional counterpart (but really, even in the pagan heyday, she was still feared because of the whole cursing thing).

You hit Crowley on the head. That bit about "the douche who spells magic as 'magick'" had me in stitches. However the cliche of the upper-class secret society of magicians goes back way further. In the early 1600s, a number of pamphlets were disseminated across Europe claiming that there was a secret society of doctor-mystic-alchemists called the Rosicrucian Order, and that they were planning to unleash revolutions in science, religion and philosophy upon the public. No hard evidence has ever been found that these guys actually existed, but the pamphlets and mysterious posters stirred up quite a panic in Germany, France and England. If they were real, they were really good at maintaining their own secrecy. But, after them, secret societies became all the rage. The 18th century saw the formation of the Freemasons and the Illuminati (who were actually atheists), the Theosophical society and the Golden Dawn came together in the 19th among many, many others. And Crowley himself was a member of the Golden Dawn prior to taking over the OTO.

The "satanic panic" was primarily caused by a gentleman named Anton LaVey and his "Church of Satan", Michael Aquino's "Temple of Set", as well as the Manson Family murders.