Mueller said to follow the money for his own case, so why cannot this case be refered to the FBI?
You can refer the case if you want, but where is the proof?
I get the desire for revenge and justice, but it still has to meet the minimal level of provable criminality before anything could be done. Since Grassley has referred three of the four to the FBI, he probably at least looked at to see if Ford could be turned over as well.