Elon Musk has used the pump and dump theory where he first lifted the price of Bitcoin and later on dumped it by calling it a dirty coin as it is an energy guzzler.
So, these dark web guys would have suffered massive losses and now they are after him.
By this writeup, we do not say that threatening by the Anonymous group is correct as they are equally doing wrong deeds and targeting normal and innocent population and asking for ransom in form of Bitcoins.