>What weapons or bombs would cause this type of charred remains and melted steel?
Can't play the video for some reason, but a Microwave radiation weapon could do this from two or more sources triangulating on a target causing it to catch fire internally. So it burns from the inside out. This is why fire lines are created and why neighboring items are not affected. These weapons create an intense fire and heat that is actually oscillating as you can see with the cars; a regular fire would burn things in place and would not move them around. Also note that these type of radiation fires do not need as much air as a regular fire due to the sources be wave propagation.