The problem is that people like Schettino and Davidson, if not making big mistakes, rise slowly but steadily through the ranks until at last they become a captain. Often these characters know very well there limitations and are masters in hiding their shortcomings on the way up. We call that rising to the surface by lack of weight.
However, once having arrived at the top there incapabilities will show immediately in case of dangerous situations where real leadership is required. They then fall visibly short as they are not equipped to exercise such leadership and take real charge.