lets face more facts..
Obviously the Capt and his F/O had either blindly follow the rules, or never before been without APU in a sunny and hot weather,
we do not even need to mention Riyadh or Death Valley.
Their initial solution to start engine first was partially good, but why they did not open as many service doors as possible, with F/A-s to guard them.
A but what about the "rules.." ?
Yes there are rules and there is a common sense too.
Open few doors would have and did have much more effect than any packs or any other tricks...