Need 10,000 bitcoin in collateral at $46k, assuming they expected this volume. If they didn’t anticipate this volume, then they would be either in violation or screwed. Maybe the MM did their job very effectively. Just surprising is all.
Discussion
Are you assuming they just bought this bitcoin?
Grayscale has been around since 2013. They have over 600k bitcoin 
Not really sure where they sourced it. Could just be all the bitcoin circulating out of GBTC - very possible. Not sure if Bitcoin held in a trust for a vehicle that is also converting to and ETF is permissible. Thats said, seems like GBTC is just milking their vehicle and fees and not interested in competing on low fees, so maybe they just accepted their fate and knew Capital would rotate out so collected on the fees? Possible I guess.