So why plead guilty? The answer is simple. Look on the net and you will see that because this case is being labelled a fraud, it would appear that investors are going to be able to claim their investment back under the US government's financial fraud protection scheme. A judge has already given his approval in principle for compensation, without any evidence having been presented and financial fraud being demonstrated in a court of law. And it would appear that there will never be such a demonstration in a court of law. Why? It would appear that all the funds financial records are mostly "missing" (rather like Dov Zakheim's US$1.4tn) and those few records that do survive are in a terrible mess.
However, since the guy has pleaded guilty we do not need to demonstrate the fraud, because he says he is guilty.
And look further on the net and you will see that these "victims" have also been told by the US tax authorities that they will probably also be entitled to claim back some taxes on these defrauded sums.