I guess they werent worried about the effects of the blast damaging the copters or something?
Syria started the conflict with something in the neighborhood of 40 attack helicopters and 60 heavy lift helicopters. Last I heard they were down to about 20 attacks, due mostly to maintenance and spare parts issues. Theyve been using the heavy lift helos to deliver supplies as the roads are mostly impassible to government supplies. If theyre using the heavy lifters to drop bombs then that is done from high altitude to avoid ground fire. But this indicates they have either lost more attack helicopters (probably to spare parts issues) or the attacks they have are over-taxed. Using the urgently needed heavy lift helicopters indicates that somebody, somewhere is going without needed supplies. The bombing is an indication of weakness and desperation. Also, tactically, how effective is a bomb of this nature? The effect will be mostly wasted as there probably arent many targets worthy of such a large device.
They're just being eco-friendly, finding a way to re-purpose those broke parts and used oil......
I think you are right. Probably one of the rebels own bombs went off too early.
I guess Syria is learning about having spare parts and stuff before wars break out.