I agree that intent is very important, but other things matter too, both legally and ethically. If you take on certain responsibilities then, well, you're responsible for them. In law that manifests as things like duties of care, as well as variations on a theme of ignorance of the law not being a defence. In real world terms, a supervisor who failed to spot a serious error that resulted in harm might not be criminally liable because of lack of intent, nor deserving of punishment for an innocent mistake, but their demonstrable lack of competence might still make it inappropriate for them to retain their position.