not that it took any great insight to get to that conclusion. Any FPV flyer who has handled and stressed Li-Ion batteries could tell you that they don't explode, they conflagrate, which is dangerous enough but looks different from what happened. They are also unpredictable enough that you couldn't get a large number to do the same thing at the same time. For instance if you tried to short them all to initiate fire, you'd have no way to know the charge state and the ones that were nearly discharged could end up duds - that wouldn't be a very reliable attack.