So you think the following is more likely to have happened than this all being accidental:
1) The ref is offered money to not only fix a game, but to injure an opposing team's QB.
2) He is ok with it morally.
3) He believes he can, without pads, a helmet, youth, or a weapon, actually injure the QB.
4) He decides to try to accomplish his mission without any subtlty, with a weak forearm to a helmetted QB's head.
Sure, it's possible. Is it more likely than this being accidental? Is it even close?