Comey says he (the FBI) did not find evidence of CRIMINAL intent that would meet the CRIMINAL reasonable doubt test, and that gross negligence in this matter is not the same as injuring someone while driving drunk, and that the DOJ has “never” used the gross negligence test in the past. Case closed in his opinion as to criminal intent and gross negligence. Comey sees this more like a Federal employment discipline matter, and everyone also knows that Federal employees are essentially “untouchable” compared to the private sector.
Also, three other issues: (1) famous person loss of reputation, if she eventually wins in court, she might have lost the election just because of the indictment; (2) interference with election for POTUS; (3) national and possibly international economic harm caused by many of the US “gubmint” officials including the President tied-up in this mess as witnesses, co-conspirators, etc.
He was trapped and just should have admitted that there is and has always been two tiers of justice, and two (or more) classes of citizens.