The Captain is always at risk, until the facts are known and the correct assessment of responsibility is figured out. After that process, from everything that's known so far, in this case the Captain is not at fault. The natural reaction as a Captain is to say "how did he(Captain) do that?" With more information you can see how it happened. If anything it highlighted areas the union has complained about for the better part of a decade. It shouldn't have happened. Everyone agrees on that. It requires an internal assessment of how it happened and the corrective actions needed to prevent it from happening in the future.