And now we learn, in their own words, that they didn't have emergency systems in place because it was a new "experimental" drill, therefore there was no safety record, therefore they classed it as 100% safe. The same kind of mindless box-ticking that gave sub-prime securities AAA credit rating because they hadn't been around long enough to fail.
This is what happens when doctrinaire capitalists regard government regulations simply as barriers to be overcome, by cheating if possible.