I've thought something very similar, regarding Comey, for some time.
He didn't do HRC any favors. What troubles me is he went after Trump, while FBI director, and continues to hound him today.
So he could have always been a Trump hater and felt he better let his feelings be known, with regard to Hillary's actions, or possibly be in a world of trouble later.
Or he is honest, trying to do the right thing and like you mentioned got cut off at the knees by Lynch? If so than what did Trump do that Comey/Mueller were willing to use some shady intelligence to continue investigating Trump?
IMO Mueller and Comey are anti Trump, found nothing on him because there is no there there.