I'm not surprised that it was the human element that caused all this. That's usually the weakest link.
Did you ever read about Stuxnet? Facinating collaboration between U.S. and Israel to sabotage Iran's nuclear program.
Basically the idea was to get a computer virus into a major Iran nuclear facility to disable the centrifuges. A huge endeavor, considering that for security reasons, the entire facility was not connected to any outside computers.
The U.S. and Israel were able to infect a HOME computer of at least one of the workers at the nuclear site...and then they waited. Sure enough, the worker brought a USB thumb drive used at home into the office, and BAM!, the virus is on the nuclear facility computers. It was then possible to remotely make the centrifuges over-spin until they exploded. Insane.
All the computer failsafes go out the window when one human goes and screws it all up.