that deer you just posted is something called a cactus buck! basically, the buck has either accidentally gotten castrated (barbed wire fences can sometimes do this) or was a hermaphroditic at birth, and due to low testosterone production, does not shed his velvet and develops these thick, multi-pronged antlers that have tons of velvet (normal bucks tend to drop velvet due to increased testosterone). It's a super interesting mutation and some crazy antlers are a result of it

this is so interesting i had no idea !! apparently deer with this condition sometimes keep herds but dont engage in headbutting or other territorial displays, and just kinda hang out with their antlers all year

so theres the one from the video

but then also stuff like

(this ones with restored fake velvet )

turns out not all deer with antlers like these are true cactus bucks though - injuries and other hormone imbalances can also cause similar growths ( and also i guess a lot of people breed specifically for huge antler mutations in whitetail deer )