https://www.youtube.com/watch?v=IaWdEtANi-0
The following summary is my own:
The whole story is shown in the first seconds: three aircraft encountering more force than a usual landing (such as a runway overrun). All three fuselages breaking into three parts in exactly the same two places! All three aircraft exactly eight years old.
Aluminum members called chords run the length of the fuselage and around the circumference to make up the fuselage structure. The chords are joined to each other and to reinforcing surrounds for large openings like doors.
Poorly fitting chords and bear plates around openings were redrilled when mounting holes were misplaced, reshaped and pounded with hammers in order to mate them. This weakened of the structure to below design margins. In addition excessive metal fatigue due to hand processing led to accelerated corrosion, likely causing structural failure in three eight-year-old NG aircraft that broke up on landing. The aircraft were engineered to survive an emergency landing intact and were designed for 30-year airframe life.
More to the story as the government colluded with Boeing to cover these deficiencies and frustrate the actions (eventually lawsuits) by a team of whistleblowers.
Basically, the subcontractor agreed to use computer controlled manufacturing processes, then did 90% of the work by hand. The resulting substandard parts were beaten into shape on Boeing's production line.
Watching this, I can better understand a recent story on local TV about developments in the US airline industry. They forecast that many companies will using the the opportunity of the pandemic to retire older aircraft.