premise: Some of the emails had the subject line, "Think Twice." They were sent from a spoofed email address. The sender claimed to have had an associate plant a small bomb in the recipient's building and said the only way to stop him from setting it off was by making an online payment of $20,000 in bitcoin.
hypothesis: The sender would have accepted $20,000 in any crypto-currency.
reason: It is clearly stated that online bitcoin is accepted.  The system may not see a difference between bitcoin and cryptocurrency.