Because in the film industry, actors are not the ones responsible when it comes to firearms. There are armourers/props, people, and even assistant directors who are responsible for on set safety, actors and crew trust other departments to do their job correctly and safely. There are so many rules and regulations for how guns are handled on set, on every set I have worked on guns were locked in a safe with the armourer being the only one with the key, they would have to have their eyes on the weapon at all times with no exceptions when it was outdside the safe. You don't hold an actor responsible if there is a stunt gone wrong or a piece of the set falls down because it isn't their job unless he was behaving recklessly or outrageously. Although he may hold some culpability due to his role as a producer and the financial stuff, i.e., budget cutting, hiring inexperienced crew, etc. I can't stand the man myself, but he is not the one who is most responsible for this incident