He didn't fight in France, and as Neville had also pointed out for her, he had risen in rank faster and higher than any other man his age. While everyone else was fighting for their life in the trenches, he was busy climbing the ladder and establishing a name for himself. Harry didn't trust him because of that. Hermione didn't get that feeling when she first met him, but it wasn't as if she had ever found him inherently trustworthy, either.