No criminal charges have been filed yet because it's not yet clear where the money went or who could have stolen it. The Madoff case didn't have this element of mystery because there weren't multiple layers of intermediaries to muddle things, and because the case was blown open directly by Madoff's confession.
Law enforcement is eventually going to figure out the answers to these questions, since they are knowable if you dig deep enough; it's just that this takes time. And then I would bet there will be criminal charges.
Bernie Madoff is rolling in his grave, his plan was just to die before getting caught.