The idea of selling things like our strategic helium supply for $460M to "pay off the debt" would be like me selling bricks from the foundation of my house for a penny to "pay off my mortgage".

$460M was for what was left after the large majority had already been sold.

In the best case, "strategic reserves" are the government speculating on commodity prices. They use tax dollars to buy a commodity -- raising the price on everyone so they can hoard it -- and then more tax dollars to pay for a storage facility, and if they're lucky the price goes up by enough to pay for the storage and the time value of money by they time they sell it again. That frequently doesn't happen.

In the common case it's the government subsidizing corporations -- including foreign ones -- by using tax dollars (at government contractor rates) to operate a storage facility at a loss so the industry doesn't have to do it themselves. Then, when they go to unload it, they generally unload enough to lower the market price on purpose, practically guaranteeing that the taxpayer is getting a below-market return. This unloading also has a statistical correlation with the election cycle (see also "strategic petroleum reserve") which is extra stupid. And the expectation that it will happen deters others who aren't paying government contractor rates from storing the commodity, so from a "strategic" perspective you don't get anywhere near as much of a buffer as you're paying for.

If the tech industry wants a reserve of helium then they should buy some land, install some tanks and fill them with helium in years when there isn't a shortfall.

What if it's not actually your house, but some unspecified "somebody else's", and you only stand to profit from it? Starts to make sense why some unscrupulous people would go that way, shitty as it is.