That crash -- Ethiopian Airlines -- is the combination of several factors.
1- a bird hit one of the angle of attack sensor, which then started reading wrong
2- the aircraft does not have the optional "AOA disagree" warning--it was even suggested that the AOA disagree warning was not even functional
3- the 737-MAX has a system called MCAS that is supposed to make the plane 'feel' like the 737-800, despite having more powerful, heavier and differently placed engines. And to prevent the plane from stalling, that system relies on a single AOA sensor, which happens to be the one hit by the bird.
4- because the system was meant to be transparent, pilots were not trained and perhaps not even told about it being there.
So there you have it: a poorly designed system, lacking redundancy, getting compromised data from a defective sensor without the crew having have the training, and perhaps even the knowledge of what that thing was doing.