It's a Confucian act. When disaster befalls the group, the head figure is expected to take full responsibility, because the head figure (ruler of the country, CEO of the business, principal of the school, father/grandfather of the home, etc.) has responsibility for the well-being of all those underneath him--or in this case, her.
For example, in 1985, the CEO of JAL resigned the day after an airplane disaster killed 550+ passengers on a jumbo jet, even though he had nothing to do with the crash. If he had been a samurai in the Edo era, he would have disemboweled himself.
Great point. Worth repeating!
The JAL maintenance chief also committed suicide.