Krav Maga teaches several different types of punch defenses which are based upon distances, angles and reaction time. This particular video is dealing with a punch where the attacker lunges at the defender from a slight distance.
If somebody is perceived as a threat, it is imperative for survival to act as quickly as possible to avoid bodily harm. With training this becomes instinctive reactive meaning, you don’t think of what you should do because it simply comes naturally based upon muscle memory and visual stimuli you have practiced.
