Something that was missed. He got his left foot out of the stirrup and on the ground at the same time he got his bicycle to a stop. He was in a stable position. Then he had trouble getting his right foot out of the stirrup and on the ground. That would be no problem if he kept his left foot on the ground. But he didn't. He took his weight OFF his left boot moving his center of gravity to his right and down he went. Look at the video again. He's stable with his left foot on the ground. He lifts it up and moves it to close to the bike as he goes down. And when TF did stirrups get put on bicycle petals and who thought it was a good idea?