If you check out the linked in profile of the Assistant US Attorney prosecuting this case:
https://www.linkedin.com/pub/michele-korver/4/405/977it seems like she considers herself an expert in the following areas:
Wiretapping and electronic surveillance
International and transnational organized crime
Digital currencies, darknet websites, and other internet related investigations
Money Laundering and Bank Secrecy Act investigations
Asset Forfeiture
I suspect that the government is just testing the waters to see how far they can clamp down on Bitcoin traders and probably considers this Assistant US Attorney as the best and most motivated person to handle the case.