Wouldn’t there need to be a huge structure to contain enough explosive gas mixture
to create such an enormous blast as this? I’m thinking an indoor arena sized
building filled with a stochiometric mixture of oxygen and fuel to
make such an explosion.
No, some gases readily form vapor clouds that are a mixture of air and flammable gas. The mixture is often the right ratio for fast burning if the cloud finds an ignition source. The cloud can float over a plant and will create a huge pressure wave on ignition. The pressure wave will crush everything underneath.