“he saw the long span bend and shatter in the center and give way”
It could be that the road deck that was being replaced HAD BECOME critical in holding the bridge together. If rust or failure elsewhere shifted the loading factors and the deck took up the slack...then they take apart the deck to replace it. Bam, it comes down.
Thank you for posting that. I was trying to think of a way to describe that, but my vocabulary fails me because I am NOT a professional.