Sounds like someone else’s fault, unless he owned and designed the system. No single engineer should be able to cause that kind of damage. Quorum rules, etc.
You have to expect people to make mistakes. I’m not saying he didn’t fuck up, but if a company is down a billion dollars the story should be of multiple people making multiple mistakes.
For what it's worth, a billion dollars for this company, while still a lot, isn't world ending. It was probably insured, too.