Because it's the DoJ prosecuting, I'm guessing (but don't know first-hand) that it's uncommon for the government to prosecute administration witnesses, even from previous administrations. Once upon a time Congress would prosecute and impose punishment itself: https://en.wikipedia.org/wiki/Contempt_of_Congress#Inherent_...
Here's a 2018 article listing some prosecutions: https://www.nbcnews.com/politics/congress/5-people-who-lied-...
Because it's the DoJ prosecuting, I'm guessing (but don't know first-hand) that it's uncommon for the government to prosecute administration witnesses, even from previous administrations. Once upon a time Congress would prosecute and impose punishment itself: https://en.wikipedia.org/wiki/Contempt_of_Congress#Inherent_...