That makes sense.I am not defending his actions, but its known that the jury felt sorry for the man, due to their thought he was the fall guy for Dick Cheney.
Another interesting point, this had nothing to do with the Valerie Plane thing, this was about lieing to the grand jury and other counts.
As the old saying goes "the cover up overshadows the crime". If he didn't cover himself up he wouldn't have had this ruling.