If they have concluded that their was some kind of fraud involved then having the government investigate and expose the facts is a lot easier and cheaper for them. They will then be free to use those facts to recover money.
They're the owners of the company; they're already entitled to their share of whatever's left.
Institutional investors are a lot more worried about the (additional) reputational damage, from having invested with criminals, than they are about recovering fractions of fractions of fractions of pennies on the dollar by raiding Elizabeth Holmes' personal bank account.
