Sometimes the gods are looking after you.
Sometimes you get stuck with a Hanzo, Widowmaker, Genji, Soldier: 76 combo. The will of the gods is unknown and I'll be damned if I'm going to spend any amount of time trying to figure out their madness.
That would include, how the hell this happened.
As I watched it for the billionth time, it seems she bounced off Roadhog's body as he fell. It was pretty epic and the player's reaction was priceless.
All you can do it thank the universe and move on with your life.