Has more to do with the nature of the impact than anything else.
Hit the ground hard enough and even a brick will disintegrate.
Russian structures are a little different in the certification (for example required to survive a doublet of the type that brought down the Airbus that was American Airlines 587)
But the observations that you have made in the accident have nothing to do with the strength of the aircraft, just the nature of the impact.
Cheers
Wino