It is possible the people in the front of the plane didn't look aft once the plane headed back to its starting point.
If the fire started on landing after a fuel tank was ruptured, the people in front probably didn't have a clue about the seriousness of the situation.
They may have been locked into the mindset of, "Let me grab my bags as we prepare to get off."
Yes, in this case such delays undoubtably cost lives, but it seems like passengers were streaming out of the front exits as soon as possible.
Passengers DO NOT train for this. The safety briefing never says, "Flee for your lives at all costs!"
Doing so would lead to panic, which is worse.