This happens from time to time. Reasons include overwhelming desire to alleviate blue-buckles without a receptive doe; overwhelming desire to assert dominance over that punk who’s rubbing his antlers on the favorite cedar; one is actually an antlered doe; one or both parties are actually homosexual and November is coming (pride month in the deer woods); one buck tripped over a scrape and fell into another buck’s bottom with his rut rod outstretched; any variety of other scenarios to be sure.
To be reasonable, it’s most likely that one is an antlered doe, or one/both bucks are open to trying new things. Antlered does usually don’t sport crazy racks but they can, and they’d have the same breeding requirements as any doe. Also, homosexual proclivities are documented in pretty much all species that we study. Look into hyenas, dolphins, and other cervids. Then read about Caligula and tell me there’s a difference…