He got away with it because he cheated and his team benefitted from it. At 18:51, as soon as the ball is cleared upfield and the referees turn to follow the ball, Lenhart casually hits Camara in the face. It is calm, calculated, cynical cheating. He doesn't think the refs will see it and he knows Camara will react. And the worst part is that he got caught and he still got away with it, because his team got a PK and both sides are reduced to 10 men for the rest of the game. That is a massive advantage. And then the disciplinary committee does nothing about it, so he gets positive reinforcement: blatantly cheat and even if you get caught, you'll help your team win.

It was awarded because it was a foul in the box.