It's never so simple as all that. But Mark Comey's intervention had a significant and noticeable effect. Even if you don't like Hillary much, then it still mattered because, you might say, it reminded voters who might have been wavering that Clinton had her own flaws.
What I found the most revealing, and it sadly rings true, with the caption to the video: "Trump's supporters saw Clinton's experience and qualifications as huge negatives". When did we get to that point, that people can legitimately think that the better-qualified you are for a job, the worse you are suited to it?!