The most likely cause is explosive decompression either from a faulty cargo door or undetected structural damage over the 18 year life of the airframe.
So you disagree with statements being issued by Russian investigators?
Show where any Airbus cargo doors have shown an inflight failure at any time and your argument may be valid. Just because some 737 cargo doors were mis-handled and the latching mechanisms of the non-plug doors were damaged causing ex-decomp in the ‘80s doesn’t mean baggage doors on an A321 will suffer the same fate.
It was an external force. Bomb or missle.
One news story had photos that showed parts of the fuselage peeled ‘out’.