Trump felt something on his ear, put his hand up like he was swatting a fly, saw blood on his hand and collapsed. No one saw any blood because it was just a "prick" - like getting your ear pierced. As Trump cowered behind the podium, flat on his face, a little bit of blood dribbled down his face. That's why those trickles of blood went from his ear to his nose and mouth, not down his neck.
On the other hand, there was a dead man and two seriously wounded people in the crowd.