For a while, you could sell $1 of crypto on the US stock market for $2. You could take a tiny public company with a stock market listing but little or no operating business, merge it with a pot of, say, $100 million of Bitcoin or some other cryptocurrency, and sell shares of the pot at a $200 million valuation. This is called a “digital asset treasury company,” and it was a great trade and a lot of companies did it, though in recent months it has largely stopped working for the obvious reason (it is dumb).

Are BTCTCs stock or more like closed-end funds/ETFs?

• they are stocks
• not pure pools of bitcoin (they have associated business lines, bruh!)
• stock investors often can't get access to crypto (jezus, how hard can it be?!), so buying stocks is great
• For a while they mostly went up, and stock investors like to buy stocks that go up.

• they are investment funds, not-very-closed ones, ETF-like
• yesyes, a little side business but mostly just ETFs
• no, stock investors shouldn't have exposure to bitcoin.
• they have all collapsed in value, so um, scratch that previous reason that they were in a paper bitcoin summer (#1217842)

Even if you think this is all very dumb — and I did, and do — the point of an index fund is to override your own sense of what is dumb and just give you the market portfolio. If the stock market has decided “hey let’s do a lot of crypto treasury companies,” then as an index investor you should own a lot of crypto treasury companies, even if you hate that.

There is considerably more money invested in stock indexes than there is in crypto, and some portion of the historical demand to pay $2 for $1 worth of crypto wrapped in stock has come from investors whose mandate was “if it’s stock, buy it.” Now that demand might fall off.