I like to think that part of the reason why Will makes eye-contact with Hannibal is curiosity. At first meeting, Hannibal reads Will almost indecently. Second meeting, he tells Will that he doesn’t thinks Will is fragile; rather he is dangerous — not implying it in the way a domesticated dog gone rabid is dangerous, but instead the way a viscious, poked at, wild animal is dangerous. Throughout s1, Hannibal keeps chanting, “Tell me, Will.” And while he claims they are having conversations, Hannibal barely tells Will anything about himself. No evidence for Will Graham to piece together, never getting to see past the person-suit. I think unconsciously, Will must have known something was off, and importantly, he was curious about Hannibal. He must have wanted to know what made the person who could know him so well tick. The only thing he could do was follow the trail of clues Hannibal’s murders left behind to the person behind the veil. I really like to think of Will as this fascinated, childishly curious person staring at Hannibal unabashedly, trying to solve his mystery like how a kid works at toy trains or a rubix cube.