There will be contributing factors listed, but the main factor will be pilot error. No one had to die, if the pilots had just followed a 54 year old procedure for how to handle a 737 behaving in that manner, as evidenced by the Lion Air flight that did not crash when the jump seat pilot saved the day.
Likewise, no one had to die if the sensor hadn't malfunctioned.
Almost all catastrophic failures are caused by a combination of errors. Designers go to GREAT lengths to make sure that one single failure (be that mechanical, procedural, or human) can cause a catastrophic failure. So the fact that human error could have prevented the failure isn't unusual.
So while I don't disagree with you that it sounds like the pilots could have saved the day, that doesn't lead to the conclusion that pilot error is the root cause of the failure. In fact, the root cause will almost certainly be the malfunctioning sensor at least based on what I've read so far.
An easy over-simplification of root cause analysis is the "why" chain. Keep asking why until you can't go any further.
Why did the people die?
Because the plane hit the ground in an uncontrolled manner
Why?
Because the pilots were unable to keep the nose pointing up during takeoff
Why?
Because the automatic pilot system took over
Why?
Because it sensed a stall condition
Why?
Because an individual sensor malfunctioned
Why?
<This is where you get the electrical engineers to figure out the root cause>