Regarding convicting criminals, there may or may NOT be proof of criminal activity, and accordingly, a better result may be to attempt to make whole as many customers as possible. We do NOT have enough information to make broad general statements to pursue one avenue at the exclusion of another, and we do NOT know the extent to which multiple avenues may be pursued simultaneously.
According to Mark, 600'000 BTC were stolen from his company, that is why he cannot pay to clients what they were due according to his terms of service. Whether he lied or told the truth, a crime obviously has been committed.
That's a good point that if the BTC were really stolen, then there is a crime. If the BTC were NOT stolen, then there was a crime. However, your earlier point was that you could give a fuck about the investors, so long as the crime is pursued.. and the wrong doers are punished.
There may NOT be enough evidence to resolve these potential criminal matters, and it would be really stupid and short-sighted to pursue this matter from only one angle....
At some point, it may be deemed to be a better course of action to discontinue the pursuit of the criminal angle, and those kinds of decisions would, in part, be affected by the existence of evidence and the willingness of prosecutors to pursue such direction in light of all developments and going forward agreements.