For the most part I agree with your other comments except these. Do you really need demolition experts or just a terrorist training camp, the internet or the local mosque supplying the instruction on how best to blow up a bridge? We seemed to figure it out quite well during WWII after teaching boys pulled from the farm fields and just out of high schools of America and sending them off did we actually have the original plans for every bridge we came across and demolished in WWII because that is not how I read the history.
Give them the basics of how to bring a bridge down and most likely they can.
How did this bridge come down could not tell you until there is an investigation, and given past events like this we will not be told if it was brought down by explosives only that there was structure failure.
Most of the bridges that we blew up in WWII were built in the 19th century or before. They were often built out of stone and mortar or in many cases wood. They were built prior to modern advances in structural steel, concrete and the ability to make concrete denser. We didn’t need plans because we KNEW that there weren’t piles driven 100 feet into the ground, everything structural was visible and we could use as much explosive as we wanted and we could put it everywhere because we weren’t trying to hide anything. AND when we blew them up, stuff flew everywhere, it didn’t just collapse down like this bridge did.