As already said, the plane had been found to be so poorly maintained during a techncial check one year ago, that it was prohibited by French authorities to fly to and land in France.
Considering the other known circumstances of this crash, this is what solves the issue for me - even more when considering that the whole airline has a history of being accused of unsifficient technical maintenance. The Yemenetes (?
) call airplanes of that carrier "flying coffins".