Everyone, including the most competent, makes mistakes though.

If single small mistakes have disastrous consequences, the system is probably too brittle. Approaching it from a blameless angle gives you a better chance of fixing it, as people will cooperate to fix the issue rather than be busy not getting fired

You can still identify and fire/relocate/retrain incompetent people, but that is better done as a continuous thing than as a response to a mishap