The engineer in me is curious as to what happened. I think I have some insight based on the structure and how it was loaded, but I am far from being a top-flight mechanical engineer, and I'm looking forward to hearing the NTSB reports on how the failure happened.
I've already started hearing blame being tossed around. Some of it's even gone political. The truth is that the bridge was inspected regularly by both state and federal agencies, and though it was reported as structurally deficient, rating a structural stability score of 50 out of 120, that is far from being considered dangerous. The construction happening was resurfacing the concrete decking, which is not a structural element (the concrete decks are free-floating and have expansion joints).
We will see. I'm also curious about how the cleanup and new construction will be managed.