It certainly wasn't the only reason she lost, and it's unanswerable whether it would have tipped the election. And I don't think it was malicious. Rather, he was bending over backwards to be scrupulous.
Still... those scruples were just ass-covering. The email servers had been investigated to death, and no charges have come of it. He knew it was nothing, and he knew that announcing it was an inherently political decision.
So I don't take any joy in seeing him hoist by his own petard, but he brought it on himself. He thought that the voters wouldn't put a criminal in charge of the country, and in trying to bolster that by following what he thought was the letter of the law, he helped put that criminal in charge.
The charge here is absurd, and so it won't cost him more than lawyer fees and possibly some time in court. Little enough to pay for a mistake that has cost us all a lot more.
We do have a problem with hate speech in society, but it's cruelly ironic to make his statement out to be such. Not being able to have contentious conversations based on reality certainly doesn't help either.