Everything that Lydia said was confusing to Isaac, because none of it was even remotely expected. First of all, and least of all, he didn't think that Lydia could ever see him as attractive. He knew that he wasn't hideous, if he was he wouldn't have caught the eye of Malia, or Ruby, but Lydia had a different 'type'. Isaac wasn't really that type.
More importantly, hearing that she saw in him what she thought Allison saw, what he hoped Allison saw, left him literally breathless for a second or two. Isaac, of course, didn't see it at all, and he did see his care for the well being of everybody, even strangers, as a weakness. To have her say it aloud, proving that she had seen it all along despite the fact that he thought he was the only one particularly aware of it, and to insist that it was a quality that made him stronger practically blindsided him. He knew Lydia was smart, and of course she was observant, but the two of them didn't really know each other until they got here. And even now, they were still learning, dancing around the fine line of friendship between the feeling that they should avoid each other and the feeling that they were obligated to not. At least, that was how he felt. He didn't want to be friends with Lydia because of either of those things; he wanted to be friends with her because he wanted to be friends with Lydia, and her simple observation was the first time she sounded, to him, like a friend.
"To be fair to you, I think it was harder to get to know me back in Beacon Hills. Considering everything that was going on," he justified quietly, letting her pull his hand away and squeezing hers before releasing it. "I think I always saw it with you, though," he admitted before he could stop himself, his eyes falling to the ground with a look that was almost shameful and still tainted with his exhaustion. "I mean, when we were younger, I didn't, but when Derek kicked me out, when I moved in with Scott and started helping the pack... I saw why you were her best friend. I mean, I saw why everybody wanted you around, you know?" His lips pressed together in a thin line for a moment before he sucked in a slow, deep breath. "I knew you were smart. I mean, I knew that for a while though, I feel like everybody did. I don't know why you acted like you weren't, but it was obvious that you were doing great in classes and stuff. But when I joined Scott's pack you were just so... I don't know. Brave. Stiles was best friends with the Alpha, he knew Scott would always have his back but you were on the fringes. You weren't treated with the worth that you deserved and you still stuck around, just to help people, and - I don't know. I guess when you spend a lot of time around bad people, the good ones shine through easily."
Isaac looked back up at her when he finished, that small frown still tugging at the corners of his mouth. "After Scott took me in I saw it in you right away. And I realized, you were braver than any of us, you weren't an archer, you weren't a werewolf. But you stuck around. Because it was the right thing to do, and nobody appreciated that." He barely gave a shrug. "I guess I care about people and you care about the greater good. That's why I hated myself for leaving. I thought you'd have people, but now that I look back I realize how stupid that was. They didn't appreciate you when you were helping them, why would they appreciate you when you needed them?"