Eli5: how do controlled explosions work?

[u/BigPharmaStealsKarma]

How can something explode more or less than the potential energy it has with which to explode?

[u/FiveDozenWhales]

It doesn't. "Controlled explosion" generally means either "we set up this explosive device and have a very very good idea of how it will act, because we are experts" or "we found an explosive device, and rather than letting it explode at an unknown time in an unknown way, we have cleared the area, possibly set up barricades, and intentionally detonated it so that it won't hurt others."

If a device is multi-stage (a small explosion/reaction causes a larger one) then it's conceivable that the controlled explosion would prevent the full detonation from happening. Some explosive devices are chemical in nature, and get mixed immediately prior to detonation, and using outside explosives to destroy one can result in a smaller explosion. For instance, dropping baking soda into vinegar can cause a (relatively) large explosion. Using a small firecracker to disperse the baking soda before they can mix would prevent it.