Isn't this the same conversation people were having with regard to Reggie's death?
Claiming (don't think it was ever proven) that Reggie had done coke and that this had weakened his heart, even though it wasn't the direct cause of his death. The controversy was whether or not Reggie had used; it's pretty well-established, medically, that cocaine use can cause severe long-term damage to someone's heart.
Remember, there were other painkillers/anxiety drugs in his system as well.
But, go ahead and believe that the bump in the head was the problem. The fatality rate for getting a knock in the noggin is SO MUCH higher than for abusing cocaine.