Good question.
Mine is, that, since this investigation is the fruit of the poisoned tree (faulty FISA warrants), why is the prosecution even pursued?
I can think of two answers:
First, it's like Martha Stewart. Even if the original basis for the investigation is questionable, they feel as if they have to prosecute prominent cases of lying to investigators (Hillary being a notable exception).
Second, the prosecutors on this case are likely Trump-hating holdovers, looking to screw anyone associated with Trump as best they can. I don't know what the accepted etiquette is on stopping runaway prosecutors in mid-case. Surely its been noticed that this has been aggressively pursued from its beginning, including the dead-of-night armed raid of Stone's home that was leaked to and filmed by CNN.
A thing or two comes to mind . . .
Fixed!