Man, what a mess of a fight. Not a fan of either guy, I don't hate them either but this fight should be redone. I can't help but feel that the only reason Costa won this is bad luck (broken hand) an accidental headbutt and an eyepoke that basically blinded Boetsch.
Broken hands are not caused by bad luck (unless it's because the fighter fell and broke it when hitting the ground or something like that). Hands break because of bad technique and/or too much excessive force. But you have to remember that the same force delivered in a punch to do damage on the opponent is also working on the hand itself.