which I heard a call to reduce mud too early occurred which allowed the massive pressure kick to occur below the well. All hearsay though so who knows. The only person that did know if that was the case was the one who got the order to change that and was vaporized during the explosion.
Because like Cesc said, this allows companies like where I work, to develop a full field to help produce the oil/gas and get it out as efficient as possible.