Theirs didn't fail, and they did have one. The circuit breaker they had that would have worked was a big red button that killed all of their trading processes, which would have meant spending the rest of the day figuring out and unwinding their positions.
Ihey were unwilling to push that button in the short time they had. If you read the reports to the SEC or the articles about it, you will note that. The follow-ups recommended that all firms adopt a big red button that is less catastrophic.
