Of course, they were fixing this one when the accident happened. The witnesses said that workmen were going at the bridge with jackhammers. I suspect that ultimately, they’ll conclude that’s what triggered the collapse.
I remember in the Army when we approached a bridge while marching we were ordered to “break step” that is stop marching in step because the vibrations from 100 men marching in step could cause a bridge to collapse. I suspect that a jackhammer, if tuned to the natural frequency of the bridge, could cause sympathetic vibrations that could collapse the bridge. I remember also back in those days 50 years ago that bridges had signs on them that listed the maximum load that a truck could carry on that bridge. I never see those signs anymore.