You're right: There have been thousands of recorded instances from the medieval and early modern periods, with the Beast(s) of Gévaudan being the most prominent example. A decent hypothesis on the decline, especially in light of your observation that this kind of activity began to fall in frequency and cultural significance in the early modern period, is the impact of modernity itself - particularly with the rapid urbanization that accompanied it. One could also attribute lessened frequency with the increased deprivation of wolves' natural habitat and their population decline in turn. Simply put, modernity drove people from where they would have the opportunity to interact with wolves, while wolves themselves declined in population. A fascinating read on American perspectives toward wolves is Valerie M. Fogleman, American Attitudes Towards Wolves: A History of Misperception, 13 Env. Rev. 63-94 (Spring 1989), where the author describes in detail how Americans moved from despising wolves for their violent potential (but more accurately for their competition with human food supply) toward an outright extermination campaign based less on that sort of need than on irrational hatred and fear, supported by myth.