imo, saying the break was "lucky" or an "accident" isn't accurate.
he trained the check to do damage. it's intended to hurt the other person while defending your own leg. it either causes them pain enough to limp, or stop throwing it for a while and in the extreme case, cause a break. chris and his team know that checking a hard enough kick can cause that kind of injury. sure he doesn't desire that kind of injury on anyone but if they throw it, he's gonna defend himself. and if the extreme injury occurs to the person throwing the kick, you can't really call that an accident and it definitely was an exploit of a skill that defeated anderson
it's like, if I throw a punch at someone's jaw, I may not mean to break it, I just want to do damage and i'm throwing it with bad intentions. if I land flush and hard, and the jaw ends up breaking, you can't say it was an accident. I may not have desired the extent of that injury, but I threw it to do damage. I think Weidman's counter to Anderson's leg strike is the same concept
Way different in my opinion. Its more like you put your fist up to deflect their jaw with the intention of your opponent hurting them self and you break it instead. Its luck. Not something you honed in on