What Nathaniel confessed was the truth and nothing but the truth. It was true that he approached Penny with ulterior motives. He approached her after learning everything about her: her likes, dislikes, hobbies, friends, family, and even her routine. He studied her to gain her trust easily.
But alas, everything he studied about her was unnecessary to earn her trust. She was a foolish woman who would trust a loser like him for no reason.
Initially, Nathaniel found her foolishness hilarious and ridiculous. He mocked her behind her back and criticized her for it. This continued for as long as he could remember, until one night, when his boss called him for their next plan, he realized he didn't want her to become a scapegoat.
Nathaniel tried to warn her, but she didn't pick up on his hints. He attempted to change her mind and send her away, but she found his warnings amusing. He tried to indirectly tell her she would be in trouble, but she was too foolish to be scared.
