1. They know that if this is true, their economy will PROBABLY collapse?
Why would a 19 trillion economy (per year) collapse because of 100 billions of gold?
The most expensive houses in the most luxurious part of Bel Air are half of that
.
Just the top ten are worth 1.5 billion
2. They are scared of their government?
Define government.
4. They simply do not care about this?
Yup. Nobody gives a damn. You shouldn't either.
It would be stupid to store all your Gold in one place, because one Nuke will render all that gold worthless, but some of Americas most precious original documents are also being stored there.
Nope, it won't.
.
Nuclear weapons are nothing like nuclear reactors, see current day Hiroshima, so the gold won't get radioactive.
Also, it will not get blown away too far since it's already underground so it will be easy to recover, as most will just liquify temporarily