You don't know that.
“If the video game didn’t exist he would have done the exact same stunt,”
“You don’t know that.”
In the biographical and autobiographical accounts written before the invention of videogames, television, and radio, there have been depictions of children doing the watch-me-pretend stunt; and there have been children seriously hurt or killed in such events.
It isn’t hard to imagine Babylonian children, upon hearing the Gilgamesh poem, turning to play pretend with their younger siblings. Before that they pretended their younger sister was from the enemy tribe their father went off to combat... stabbing her with a makeshift spear. Before that, children pretended they were the wild tiger they were warned to stay away from... pouncing on their younger sister and pretending to rake her with their pretend claws.
All stories come first in the imagination, so before any story was ever told people have been playing pretend. ‘Watch me show off for the others by doing this - oh no I accidentally killed someone’ is as old as man.