If I understand the situation correctly Vinnik wasn´t even involved in the MtGox hack.
However, he was the mastermind behind BTC-E, which was used to launder the coins
obtained in the hack.
Many experts believe that they really did this in a clever way and that even many coins
on legit exchanges like Kraken or Bitstamp are actually coming from the Gox hack. Tracking tools
for analyzing the blockchain weren´t as sophisticated back in the day as they are today and this
makes the analysis even more difficult.
That's why BTC-E was taken down because it might be one of the gateway of the tainted Mt. Gox hacked coins. However, it has to be proven and I remember that someone has put up a good timeline as to how Vinnik or BTC-E was involved here. So investigators have their hands full in this investigation and since Vinnik already admits his guilt its not a matter of time before authorities will have the complete picture as to who really is behind the Mt. Gox hack and other exchanges (knowing and unknowingly) involvement.