I am looking all over YT for why he did it but I can not find why.

I am a Wings fan and I HATE, HATE, HATE Crosby! And I am wondering why all the replays I found are right before Crosby gets hit from behind. And because Crosby is such an _____, I am wondering if he did anything right before Schenn hit him from behind? If Schenn is the kind of player to hit Cindy Crosby for no reason, then so be it... But I doubt that any NHL player would do that for no reason, like all the highlites are trying to imply.