Ya, common misconception about the power of explosives.  They tend to release even less energy than a good fuel.  They just release it faster making a high enough peek energy density to mechanically fracture a target material.

If one computes the area under the curve of a the energy release from:
 - a pound of C4 detonated
 - a pound of C4 lit on fire to heat an MRE (Meal Ready to Eat)
it will be similar.  It's just that the peak value for the detonated curve will be much higher.

We use a slower explosive like ammonium nitrate for cratering charges which tends more to heave rather than shatter material.

Looked at another way, I could move a lot more dirt with 40 pounds of diesel fuel and a bulldozer than I could with a 40 lb cratering charge.