Unreal (although perhaps premature, since all the info isn’t out).
The 787 Max was a bad design. Placement of the engines on the wings was different, which causes the plane to want to go into a loop when accelerating. So to compensate they added software to offset the tendency. But the software depends on accurate data from a sensor, which tends to give incorrect readings. IF YOU PAY EXTRA when you buy the plane they add redundant sensors to help compensate for this and give the pilot a warning that they may need to take over control.
The problem was not well documented in the operating manual/problem checklist, and not all pilots were required to be trained in the fact that the software feature was there and could kill them. Several pilots had encountered the problem but were able to regain control, but FAA obviously didn’t respond effectively. Meanwhile Boeing was working in the background on a software upgrade.
Classic display of James Reason’s Swiss Cheese model.