Guy posting says it’s atomic, but I think it was thermobaric.
Thermobaric bombs, also called aerosol bombs or vacuum bombs or fuel air
bombs, have to deploy their cloud of fuel in a large area to mix with the air of
the target area, setting off the additional shock of the a pop of a huge vacuum
bubble once all that air and fuel transform into light and heat and a bit of vapor
and soot. Such bombs tend to come in a LOT slower than this missile, in order
to have time to spray out and atomize their fuel load into a nice big cloud, well
before ignition.
Whatever this was, it appears to have punched fast and deep into the ground
before it popped.