The article states,
Naval forces used a remote-controlled device to try to "deflagrate" the bomb - a technique that if successful burns the explosive charge without causing a detonation, the deflagration process turned into detonation.
How would they attempt to deflagrate the bomb, and why would the process then fail and cause an explosion?
Deflagration and detonation are two ways energy may be released. If the combustion process propagates outward at subsonic speeds (slower than the speed of sound), it's a deflagration. If the explosion moves outward at supersonic speeds (faster than the speed of sound), it's a detonation.
While the action of deflagration is to push the air in front it, objects do not explode because the rate of combustion is relatively slow. Because the action of detonation is so rapid, however, detonations result in shattering or pulverizing objects in their path.