Almost all airline accidents in modern days are "freak" accidents, but I personally consider AF447 one of the freakiest of the freaks. The long wait to figure out what was wrong probably amplifies the feeling.
Thats why this crash bothers me. A design flaw in a production aircraft is not something you expect in the modern age.
A combination of route planning, misunderstanding of what is happening, CRM, poor UX, and at the end, incompetence were also a factor.