That may or may not be true. CBS is reporting that the FBI backed off when the leadership said they'd take care of it.
Anyway, that's not important. Hastert would not have conducted a criminal investigation. His standard of proof would not have been "guilt beyond a reasonable doubt". Furthermore, Hastert wouldn't even have to find a crime -- only that Foley violated House rules.
And what the FBI did or didn't do has no bearing on whether or not Hastert did the right thing.
And we are to believe CBS because ...?
Are you incapable of reading prior threads? No member of Congress, House, or even the president can order or ask the FBI to stop an investigation. Where have you been?