[...] Who knows what lays hidden in mines and tunnels in some of these Eastern European countries that were occupied by the nazis during WW2.
Easy answer: death on a stick.
Say you are a nation that up to a year or two back thought they were going to rule the world, but now realise that you're looking defeat in the face AND, due to your fellow countrymen's racist habits are looking at pretty much everyone else in the world hating you for decades. You have a load of valuables on a train, which you want to hide.
First thing you do: make sure some of the locals know that there's a train-load of something very important hidden in that tunnel over there, which you helpfully signpost by blasting the tunnel entrances, having first booby-trapped the rest of the tunnel and the train very thoroughly indeed.
Second thing you do: hide the valuables somewhere other than in the train, which remains as an object lesson in why digging out old Nazi tunnels is a bad idea.
Third thing: scarper somewhere safe and come back when the coast is clear to dig out your ill-gotten gains.
Which most of the escaped Nazis never did, and instead died in Argentina, if they didn't escape the Neuremburg trials.
This is likely why the discoverers have made such a song and dance about the discovery. They know full well that the tunnels will be unstable to this day, and after the unstable sections are bypassed, you're still faced with live booby traps, unexploded ordnance, and goodness knows what else up to and including various military toxins including phosphorus incendiaries and smoke (deadly in a confined space), and a train that may or may not have anything worth salvaging in at all.
In the circumstances, it is much easier to let someone else do the difficult, dangerous bit whilst you take the glory, the book rights and a small share of the gold if there is any.
