Who knows why they applied rudder but I do know that the technique taught is rudder to prevent further wing drop. It's my opinion that people over kill this technique. I won't be using rudder in a stall. I'm not touching it.
Except if they didnt have time to realize that their ailerons are ineffective due to high alpha on the apex of the climb and the only way of getting this nose down was the rudder, or they would fall vertically straight down still with high pitch attitude.