John: the question, then, is why does Fitzgerald want Libby to face serious jail time?

If you are a prosecutor, you stack an indictment like the one Fitzgerald structured with enough charges that add up to enough jail time and financial costs (Libby faces as much as $1.25 million in fines) to achieve one of two things: truly punish the individual, or use that person to go after bigger fish.

Fitzgerald is after bigger fish.