First they have to figure out what the fuck is killing them, depending on how it's used an explosive doesn't really explain what it was beyond being an explosive. A short fuse grenade duck taped to the inside a door doesn't leave a lot after it's gone off, sure you know Frank the evil wizard is at best screaming in agony and missing a limb after an explosion but beyond that? Also it's kinda a trope that evil wizards are technophobic and only want to rely on their magic, the ones who don't are often the dangerous ones though in a lot of media they are also hermits who want to commit crimes against nature in peace.