I agree. The Russians will never admit to it, though. That is the reason they have been fairly quiet while the US and France and Egypt claim to have all the answers.
Could be poor maintenance, but it would not surprise me if it was also a bomb, considering that part of the world, the Middle East.
My thoughts are with a cargo door not secured properly. There by having a effective opening of airframe, similar to this Hawaiian plane.
https://www.youtube.com/watch?v=8NWW77HnGTc