It's about setting it aside for the gods' use

ḥerem may often involve destruction, but “destruction” is not the essential meaning of ḥerem because not everything that is ḥerem is destroyed. ḥerem occurs first, and because the thing is ḥerem, therefore the thing must be [blank], where [blank] is typically (but not always) some variant of “destroyed.” The comparison with the Hittite document here demonstrates what ḥerem signifies (removal from human use) and why therefore the destruction is necessary. The Hittite king Mursili levels a rebellious city and offers the site to the god Tešub as a pasture for his bulls. Because the god is using the site as a pasture, nobody else can use it for anything; this is the thrust of the imprecation directed at “[whoever] … will take the grazing-land away from the bulls.”— The Lost World of the Israelite Conquest, 171