As someone who is an old pilot and and not a bold pilot I suggest it comes down to being complacent. Auusie Croc guy Steve Irwin was over the hump where he no longer feared death because he "knew it all". Aeroplanes are like crocs...very docile but with a big bite when you are not expecting it. This laid back crew were bored and neither captain or co pilot thought there was anything out there to bite them. Tired, bored, complacent...call it what you like. This and the MK accident at Halifax are both down to one thing. PILOT ERROR
At least the MK crew just took themselves out!