Nice materials science explanation. But, I was waiting for the lessons learned part 
One of the consequences in engineering was the motivation to develop non-destructive testing methodologies.
The tragedy uncovered by the investigation was that during routine inspections the failure of some steel bars was observed. But, the interpretation of the observations was deeply flawed. Instead of calling for experts or sending the steel to the lab for testing, the recommendation was to weld the broken element and call it a day. Some months later dozens of steel bars failed and full collapse.
It’s understandable that at the time no one recommended an expensive lab test. Also, it’s too easy to recommend 40 years later for an ultrasonic assessment of the steel bars in place. But, that’s precisely the lesson learned. No matter how careful is the selection of the construction material was, certain structures need safety inspections, and the inspections must catch hard to see problems.
It’s great if new buildings are better designed, but we still use a lot of old buildings. So, we have the toys today to do better inspections. Once again, that’s the lesson learned. Not material science, but the proper management of existing structures.