Said permit is mostly irrelevant. The load being carried was oversize, and it is the responsibility of the carrier of an oversize load to ensure it can clear all obstacles along the route.
The clearance on the damaged bridge was not posted, because it doesn’t have to be posted. The minimum clearance was 14’6″ on the right side of the right lane. By law, clearances only need to be posted if they’re under 14′. The load was thus oversize at least in part because it was over 14 feet in height and signage alone could not be relied upon to ensure the load cleared. Interestingly, the span is high enough in the center that the load could have cleared, had the truck taken the left lane and used it while crossing the bridge.
Pilot vehicles come equipped with poles which are extended to the maximum height of the overheight load they are escorting. At least one witness says he saw the pilot vehicle’s poles hit the right side of the bridge girder before the load made impact. Alas, the load was apparently following the pilot too closely to be able to stop or change lanes in response to the pole hitting the bridge.
In short, it seems pretty damn obvious who’s at fault for this, and it’s not the state DOT for issuing a permit.