Earlier quoted context omitted.
Because he defrauded them in order to get their 3x return. Put simply, if I burn my house down in order to collect the insurance money, I've committed insurance fraud whether or not I pay that money back, and no amount of profit on the payback negates the illegality.
Although, interestingly, he didn't steal their money, he lost it in a bad trade, which is probably (maybe?) covered under the risks associated with the fund's operation. The deception was not telling people their money was gone (and also lying somewhat about details of the fund initially). Given that the loss was an accident that he didn't profit from, and that he worked to repay the money, there's a critical differe…
That said, I agree that my analogy was bad, and I wasn't trying to assert that Shkrelli deliberately set the house on fire as much as I was just looking for an appropriate analogy of something that is illegal even though it did not have any financial damages.
The point was that while damages from fraud may be financial, the fraud is the damage, and the lie is the crime.