a professional pilot with some degree of experience
...does not necessarily infer a 'competent professional, with some degree of knowledge'
In a previous job, I was unfortunate enough to encounter an experienced co-pilot, with an ATP from the FAA along with another from his country of origin. His understanding of fuel capacity, management, reserves etc are eerily similar to many of the failings highlighted in this case. That attitude complemented an equally cavalier attitude by the management towards aircraft maintenance. Sadly, it matters little how much you pay for the aircraft (new and fairly prestigious in our case) and the staff, or the value of the contracts; if there are folk involved devoid of integrity or genuine knowledge, the tragic outcome is likely only a matter of time and luck.
one phrase that keeps coming to mind as I read this is 'normalisation of deviance'.