Why are they not claiming credit?
Either:
a) As typical of most martyrs, they believe they will find their reward in heaven.
OR (more likely)
b) This is a dry run for a much bigger “event”.
Combine this event with the Buenos Aires bomb scare a few days earlier— both on flights originating in Paris — and one might surmise that an operative in Paris is pre-planting bombs for return flights to Paris. This would mean the martyrs sole responsibility is to detonate the bomb.
OK, I didn't believe this was terrorism because no one claimed credit, but you point out a very possible reason not to claim that credit. Frightening.
My initial thought was that the “bomb threat” was designed to:
A) Test for reaction/procedure taken by security
and/or
B) Test to see if they could locate a dummy device.
Once it was clear they couldn’t find anything, these guys boarded the ill-fated flight a couple days later and did what Richard Reid couldn’t finish. Maybe not a shoe bomb, per se, but something they could detonate while on the plane.
I’m still open to the “mechanical” explanation, but if so, the presence of these two on the flight is an incredible coincidence. If there were no bomb threat previous to this, I would lean towards mechanical, but the details are pushing towards sabotage.