I consider this accident to be quite simple (although as usual, there was a 'chain' of events). Divinding it in two, the first question is how did they get to the loss of control and the second is what was done (or not done) to correct it.

Although sterile cockpit procedures were broken, my understanding is that from the time they began configuring for the approach to the activation of the stick shaker, there was relatively little if any violation of sterile cockpit (perhaps a couple of minutes before the shaker). It would seem to me to be a simple lapse of attention at a critical time (no one was truly the "PF" ((pilot flying"). Our beloved god Sully also broke sterile and from my observation jumpseating and flying, perhaps 80% of crews do. I think the first question of how they got there truly had little to do with 'sterile cockpit' in and of itself. Fatigue and illness seemed to play as much or more of role of this first question then sterile cockpit issues.

The second question is the problem, in that the recovery actions were opposite of what was required. That seems a aptitude/training/proficiency issue, but to what degree each on influenced this act may never be accurately determined. Maybe there was something that wasn't identified. Perhaps the captain moved his seat forward for the landing and it didn't latch and slid backwards when he rammed the power levers forward ?

The perfect sterile cockpit in my opinion will likely never be uniformly maintained regardless of this accident. Since then, I've observed no real changes there, yet I see crews not flying exactly to its letter, completely involved with the aircraft they're flying and their situational issues.