If you look at the design of the bridge, there doesn't appear to be enough protection around the support column to prevent an impact. Even slowly moving, that vessel has a helluva lot of mass, therefore the impact force would have been immense. Shipping has changed in the 30 odd years since that bridge was built, and it was probably never imagined the size of vessels that would be used near it. More dolphins should have been in place to prevent ships from coming near the bridge. And the design itself, being a truss bridge, would have also been an issue.
Most people will not remember when this bridge, the Sunshine Skyway Bridge, was taken out by a vessel accidentally hitting a support column over 40 years ago. Since then, dolphins were put in place to prevent another incident.
If they build a new bridge, I'm guessing it will be a cable stay bridge, with the span being a lot wider, so the support columns can be placed closer to the shore.