For discussion, what's wrong with the statement "if you hold a money market cash position [you hold] the same thing as Bitcoin [or a crypto ETF]"? Or, say, you hold one of Vanguard's Gold ETFs. (Good faith)
Instruments in money market are of the kind of: "give me 100$ now and I will give you 101$ 3months later". Bitcoin is not backed by such contract. It's only backed by the hope of finding a bigger sucker later.
I'm pretty sure there's a lot of evidence that gold is a great inflation hedge but otherwise doesn't offer much in the way of returns on a long run basis. Which is a reason in various cases to hold or diversify into it over a money market fund (essentially over cash). That said, currently crypto has not proven itself to be either much like cash or much like gold.