A panic needs a script, and the Malleus Maleficarum wrote it. Published in the German city of Speyer in 1487 by the Dominican inquisitor Heinrich Kramer (a co-author, Jacob Sprenger, is named on the title page but probably contributed little), it did something genuinely new: it fused an elaborate theology of witchcraft with a practical legal manual for prosecuting it — how to investigate, how to interrogate, how to extract a confession, explicitly endorsing torture and urging judges to relax the normal rules of evidence. It also argued, at length and with venom, that women were far more susceptible to the Devil than men, hard-wiring misogyny into the machinery of the hunt.
Two technologies made it lethal. The first was the printing press: where an earlier era's superstition would have stayed local and oral, the Malleus was mass-produced and reprinted for nearly two centuries, becoming the template that later witch-hunting manuals copied. The second was institutional cover — Kramer leaned on a 1484 papal bull (Summis desiderantes affectibus) and a faculty endorsement to lend the book authority, some of which he appears to have inflated himself.
It's worth being precise about the Church's role, because it's often flattened. The Malleus was never an official Church document; the Inquisition later distanced itself from Kramer and some authorities rejected his methods as excessive. But the disavowal came too late and meant too little. The book had escaped into the world of secular courts and local magistrates, where for generations it functioned as the operating manual for judicial murder. A panic that might have flickered out instead had instructions, in print, that anyone could follow.