He always thought that men having penises was a stupid thing. Men evolved to have a strong and aesthetic form to protect the weak and the children from damage caused by dangerous predators.
Man has greater muscle mass, stronger bones, more resilient skin, and more durable feet. But nature thought it was a good idea to place a fragile reproductive organ in this body.
Women on the other hand have an overall more fragile body, with more weak points but have a perfectly protectable reproductive organ.
It was stupid men are the ones who would have a vagina and women who should have a stupid penis.
So he quietly changed it, from this day women have penises and men have vaginas and to don't have worldwide panic he will alter history as if it was the case since humanity existed.