Oh, I have no interest in excusing it. Comey apparently did, however. So either he had a personal/political/job security reason to not pursue (very possible), or he honestly believed HRC's actions didn't rise to the level of criminal behavior that you describe. I have no idea which, and we may never know.
But the Constitution (that thing they all claim they're defending and protecting) says "innocent until proven guilty"; so, like it or not, she is guilty of nothing, at this time.
Am I not bothered by this? I should be, but I'm not. Cynically, I assume that similar levels of rule-stretching, rule-breaking, and illegal actions have been going on since about 12 minutes after the founding of the Republic, and is just part of the grease that keeps the machinery of government running. Then too, I also suspect that much of what is marked "Classified" gets that way merely to hide things people want buried.