I find it very odd that the main structural support in the center is nearly obliterated. Is there any details about the explosives used?
Notice that support is a straight column and not a V-Shape like the others. Cantilevered bridges almost never fail from the center support like this, it's usually at the outstretched ends. Something isn't adding up. Only thing I could think of is a major stress fracture in the concrete but the way it crumbled doesn't suggest that imo and doesn't add up. Weird.