Ouch man that has to hurt, does not look infected though. Deer will never cease to amaze with their ability to survive.
I would guess hit by a car or motorcycle as jumping in the air breaking both ankles or lower legs. Just a guess, but holy man that's amazing that this is even possible.
Hard pics to look at, can't imagine the pain it went through. My guess would be hoof rot of beat EHD but back hooves were destroyed and slowly wore away. Just guesses.