But that's the point!

"[...] petrol, gas etc make for an excellent, photogenic fireball"

Exactly. Guaranteed plenty of publicity, but didn't actually hurt anyone (apart from the odd would-be bombers, of course). The instigators can claim that no real people were hurt during the making of this film. Just the thing to please the "boys back home" (Islamist mullahs) without causing undue guilt or second thoughts amongst the future AQ candidates they're trying to fill with fire of their own.