Thermite isn't explosive--it's incendiary, highly stable, and requires a lot of heat to light mixing the powder together creates no reaction you need a magnesium fuse or a blowtorch to get it going otherwise junkyards full of the stuff (scrap metal piles iron mixed with aluminum oxidizing in the elements) would catch on fire on a regular basis every time you had a spark.
Thermite is useful in welding and cutting in places where normal equipment cannot gain access, but requires a pretty hefty amount of energy to ignite and you would have to have at least a couple hundred pounds of it in the right container to make it actually explode the material itself doesn't, gunpowder doesn't explode on it's own it burns rapidly too. It's where you stick it that matters.
Even harmless grain used for food is a potential threat on its own using the reasoning given here. Put it in a container it kicks up enough powder inside that container add one spark and Kaboom! That's why you don't hear of those big grain towers catching fire in the mid west but rather exploding very loudly.
Improper storage of almost any substance creates the hazard not the substances themselves.
This is excess materiel from the Bush/Cheney days. Since everyone knows that they personally planted all the thermite in the Twin Towers, they had some left over and decided to sell it for a profit. Which should be illegal, since this is government property.

The first time I heard of loose change I thought it was a story about panhandlers (likely mentally ill), then the first time I heard about zeitgiest I thought it was a story about neo nazis (definitely mentally ill).
Turns out it was a total different group of crazies completely but still likely to eventually wind up in one of the two other categories--either ending up sleeping under a bridge with a baseball cap lined in tinfoil, or hold up on some mountain compound surrounded by cops.