Video of the FL bridge collapse suggests either lack of, or inadequate, steel reinforcement. It broke up like a dried out butter cookie, no twisting of structure or stringing together of parts. The engineer called in his observation of cracking just before collapse.
Lawyers going to be lined up around the block for this one.
Why would they need engineering when they have feelings and diversity to support the bridge?
Here is a 10 minute video by the guy that did the Oroville dam updates. He gives a background on the bridge and what the likely failure was. A quick summary of the failure is the trusses at each end of bridge had to be adjusted after the move. The original design called for the transports to be under both ends. Since they moved the transports closer to the center of the span, they had to adjust tension in the outer trusses for the move and then change them back once in place. It was during this process when the bridge failed.
https://www.youtube.com/watch?v=GxQJj8D_FE0