Young males are driven to learn to fight. It is a skill that must be mastered if they are to ever achieve the success that instinct propels them to do: Win females and breed the next generation of wild horses.
Watching the young colts mature over the last seven years has been interesting for me. Horses have distinct personalities just like us, and many lack the aggression necessary to fight and win in the real battle to win and keep a mate.
This young male may be starting a bit too early but his aggression will payoff, I think he will be at the top in about four years.