why exactly did he go down?
'cause #3 was shortening the gap to quick. Then he appears to think he can slow down by putting his left foot down before braking or avoiding it all together. And he was dragging his right foot before he put out his left.
Long ago the wife of a friend of mine rode through his saddle bag at a right on red. She anticipated he had pulled away when he hadn't. Funny how she blamed him for not moving.
Inexperienced riders make more dumb mistakes then experienced riders and are much more dangerous in group rides.