I have, in my opinion, a good answer for this.
Early, computer models were not possible. No one knew Comets would burst in the sky because squared windows caused extra fatigue.
Fly by wire tech was young and untested in commercial a/c. Who knew autopilot would overrule the pilot? Since then the a/c has flown amazingly. That was a test flight of an early prototype (right?). The plane was sound. The plane crashed due to software.
This time, you have the first post soviet russian a/c hitting the market. It is going after a niche market. The plane has early issues with its landing gear... gets fixed. Now you have a supposedly working plane pick up prospective buyers and fly them into a mountainside. As of now, without the black boxes, we can only assume what happened. But, the limited market size now coupled with these incidents and from a nation with a less-than-adequate history of making commercial a/c will now put substantial on Sukhoi. As mentioned above, that engine may be offered on Western made a/c. That would kill Sukhoi.
Again, my opinion