Someone could have put stuff in the road, or maybe even gotten to the truck beforehand and sabotaged it.
With something this big, I think they will find a portion of it, and the people who did it.
Anything more than one person will be found out. One or more will be careless.
Even if the truck had been sabotaged, it still would’ve had to be someone who knew about the gold. It sounds like the thieves must’ve known what they were looking for.