I'm somewhat amazed at the apparent broad based assumption that the MCAS is in fact the root issue in the crash. No question that it's potentially a significant "hole in the cheese" but there is a very really underlying issue. It's abundantly clear that for some reason the crew failed to follow SOP specific to power and pitch settings. Without the CVR we have no real insight into the cockpit CRM and the crews intent and/or issues. Was the apparent decision to try and maintain 5,000 a by product of another technical issue or was it undertaken for a specific reason. Did the plane suffer a structural issue do to overspeed (late flap retraction?)? Was the technician in jump seat, if so what was his interaction with the crew and did it effect the outcome adversely?
All we know for certain is that for the three previous segments the technical issues were manageable and addressed with the existing protocols. On this flight we have clear evidence that those protocols were not executed in a timely manner but no real understanding of why. If in fact this is the first clear incident of a Boeing plane succumbing to "what is it doing now" then we've reached a point where both major manufacturers have reached a point where "safety kills", however it is entirely possible....even probable that the root cause of this tragic event lies at the decision to deviate from the proscribed SOP for this malfunction (UAS) even if in fact it was a compound failure. What if any specific difference occurred in comparison to the previous flight that appears to have suffered an identical initial "upset" before recovery and successful completion of the flight???