I do not understand why the criminals ask for bitcoin. bitcoin is traceable. Why not use Monero? It is anonymous.
Bitcoin is 'pseudonymous', your pseudonym (address address) is fully traceable, but with the right precautions you can avoid linking it to your id. Bottom line - you could exchange it anonymously for cash.
Monero is not very popular, there's limited number of places where the victim could quickly buy XMR for fiat. It would probably be easier for hacker to take BTC, convert to XMR, then back to BTC and cash out.
But anonymity of transactions is not the key issue here, not getting identified when exchanging to fiat is.