I know that many medieval people became extremely religious and devout to their Christian faith in order to avoid the plague (since they thought that God was punishing Europe for their sins).
However, did the opposite ever occur? Did anyone in Medieval Europe thought that the pagan Gods were punishing the people for converting away from their traditional beliefs?
I can't answer about paganism per se, however, in The Decameron, Giovanni Boccaccio wrote that in Florence, "With so much affliction and misery, all reverence for the laws, both of God and of man, fell apart and dissolved, because the ministers...were either dead or ill like everyone else".
There is no mention of any sort of paganism gaining even the slightest bit of traction in Florence however, just that people stopped obeying the laws of god.