Interesting to speculate on what happened there…
The backhoe boom would have been facing forward and angled up slightly.
The fold in the boom hit the edge of the bridge just below the stepped out section.
The force of the impact flipped the boom back and up, through the deck of the bridge.
It also forced the machine downwards, crushing the trailer.
The sudden braking effect on the trailer sheared the truck to trailer coupling.
So, in answer to the original question, in a way, it hasn’t sliced the bridge in half, it’s punched a hole through from underneath.
Still some impressive physics going on there though. 😀