Qoute from that link,way back 2014 IRS made an announcement that crypto's are defined as a property and not a currency. So as such they are entitle to pay thier taxes as property owners.
Personally, i doubt if this is the reason behind the crash, i don't see any way that IRS can be able to enforce this going by the decentralization of the system, they are just blabbing if you ask me.