While often the SEC will reject ETFs that are over-levered, given such products are higher risk instruments, there was no indication that this was a factor in the SEC’s decision to reject these varying ETFs. According to SEC documents released by the commission’s office, the primary reason for the rejection was that none of the exchanges that these products were to be listed on was able to provide evidence that a bitcoin spot market was free of fraudulent and manipulative practices or that a bitcoin futures market was of significant size to satisfy this requirement for regulatory oversight.

https://tradeblock.com/blog/the-current-state-of-a-bitcoin-etf-sec-announcement-and-xbx-price-performance