How Mueller is above being himself indicted is beyond my comprehension.
It looks to me like a McMaster conviction or guilty plea is the goal here.
Any obstruction of justice charge against Trump will hinge on McMaster being convicted of something. Comey is the one who made notes on a meeting about McMaster and leaked them in order to trigger a special prosecutor for obstruction of justice aimed at the president.
This is not a “Russia” special prosecutor, it is an “obstruction of justice” prosecutor.