The many holes in the layers of swiss cheese certainly lined up for this sad accident but it emphasises that if you compound one weakness with another (poor position of the fuel shutoff, rubbish harnesses, single engine over the water at dusk, poor flot gear design etc etc) you are asking for trouble.
Sadly, the justification for many of these weaknesses is cost and keeping people in a job. In this case the people with their jobs survived and those paying the 'cheap' price for the flight paid in the most expensive way possible.