Historically, the premium has been due to the false narrative that GBTC is the only available pure-play way of gaining exposure to bitcoin in an exchange-traded vehicle.
DISCLOSURE: I/we are short shares of GBTC, and long a basket of cryptocurrencies. (The hedge isnt purely bitcoin because we believe Ethereum and certain other cryptocurrencies will outperform bitcoin.)
It isn't a false narrative if it is true. For most people, including myself it IS the only exchange-traded exposure for bitcoin you can purchase.... It doesn't matter that some small subset of people can buy euro-traded bitcoin assets... that is nonsense.
At least you disclosed that you are short GBTC.
GBTC will trade at a premium until alternatives show up in my trade account, why? because I have money in my account that i won't take out because of tax advantages and I want BTC exposure, so I have one choice, pretty simple. NOT fiction.