How did they do it? Well, if the rest of the pictures ever load... :sleep: (I have about half of them.)
Judging from the photos, they had the Hyundai excavator on a low-boy trailer, rolling down the highway at a good healthy 45-MPH plus clip...
Looks like the main arm of the excavator was sitting up just a little bit too high - the impact with the leading edge of the overpass (on the right) flipped the loader arm up and over (which would not be good on the structural components or the hydraulic systems) as the arm punched and ripped through both layers of the concrete - bridge support box beam and the roadway slab.
Meanwhile, the trailer bed is disintegrating from under the excavator with all the stress on it, and the trailer has ripped loose from the tractor - the kingpin and/or the hitch between the bed section and the gooseneck tongue section of the Lowboy aren't going to like the sudden shock, it looks like the loading latches between the bed and the gooseneck broke first...
This is why you measure the load height, and when the sign says 14' 2" Clearance Ahead and you know your load is 14' 9" you get stopped in a hurry.
If you are above the "standard height" for trucks which is 13' 8" in the USA, you send a pilot car ahead of the truck with a set of measuring staffs and feelers set to the load height, and if a feeler touches the bridge it sets off an alarm. And then the truck has advance warning to take an alternate route.
I'm darned surprised that the bridge is still standing with that much of the bottom web gone - that's the part that is in tension.
Of course both roads are going to be closed till they shore up the bridge, and that road above is going to be closed till the bridge gets rebuilt