A culture that recognizes that competent professionals make mistakes and acknowledges that even competent professionals will develop unhealthy norms (shortcuts, "routine rule violations"), but has zero tolerance for reckless behavior.
As has been said, yes, just culture.
Not a large aircraft operator myself but find it hard to imagine it is not common place to have loose articles on the flight deck. If it can go wrong it will go wrong and this incident has highlighted an area where this is the case. We can learn from it, design can be improved, loose article procedures tightened up.
Clearly some on prune are perfect aviators