The clown's impact on the children of Welcome to Derry shapes them long into adulthood, twisting them into the very adults who keep the community's pattern of animosity ongoing. The creature finds easy targets on children from broken homes — children who frequently mature to repeat the identical behaviors as their parents. However, the Hanlon household distinguishes itself as one of the few family unit that never splinters, which may explain why Mike Hanlon, even after electing to remain in Derry, persists as the sole member who never fully falls under the clown's influence.
In episode 4 of the series, Leroy finally becomes increasingly conscious of the paranormal entities surrounding the community, especially when the entity starts haunting his son, Will Hanlon, during their angling excursion. The Hanlon family comprises some of the few grown-ups who are cognizant that things are not right with the town, notably the father, who was shown to be sensitive to the Shining when he was capable of sensing Dick Hallorann's use of it in episode 3. Subsequently, he sees one of Pennywise's signature inflated orbs outside his house. The ability, alongside his inability to feel fear, along with the base of his household, may be why he's capable of perceiving the entity's manifestations. However, consider if that shining is hereditary, and one of the reasons Mike is among the few adults in the town who resisted succumbing to the town's malevolence?
Will is part of the group of children at his school being terrorized by Pennywise. All his school friends come from broken homes, with caregivers who don't believe they're being haunted. The reason Will is being haunted is because of the cruelty of the town, paired with his likely receptiveness to shine, which renders him vulnerable. This family are ultimately outsiders in the town during the early sixties, which lends itself towards the family sensing something is off about the town from the onset. Additionally, they possess a good foundation that isn't fractured, in contrast to the residents who originate in the area, with relationships that have deteriorated within.
Drawing from the It novel, we understand the young Will will find himself at the infamous nightclub, where the psychic will rescue him from a fire that the town bigots of the community will ignite. In the 2017 film, we see that he has a son named Mike and that Will eventually perishes in a configration, with his father outliving his own child and adopting his grandchild. The public account in the motion picture is that the parents were on substances, but now that we see him in the series, that's hard to believe. Maybe the shy youth, once he grew up, turned to alcohol to rid himself of the hauntings, or maybe the rotten environment got to him initially, with the KKK ultimately completing the task it began long before. Whether through the terror of Pennywise or through the cruelty of the town, instigated by Pennywise, the creature in the end achieves the last laugh on him.
These occurrences would explain how Leroy transforms so drastically from what we see in the first film and the prequel. In his later years, Leroy seems bitter and much harsher with his discipline. Since he survived his own son, it's understandable to observe such a profound shift. However, his statements hold greater significance since we are aware he's witnessed Pennywise's hauntings and the impacts they had on his son. In the opening scene of It, we observe the boy hesitate to use a bolt gun on a animal at the family property. His grandfather chastises him for hesitating and offers an metaphor that leads to a survival-of-the-fittest situation.
“There are two places you can be in this world. You can be out here like we are, or you can be trapped inside,” he says as he points to the creature. “You dawdle hemming and hawing, and someone is going to decide for you. Except you won't know it until you feel that projectile between your eyes.”
Looking back, this could represent a bit of prediction, something he regrets not imparting to his own child. Perhaps he desires he had acted differently in his youth, but for certain factors, he was unable to avoid the repellent attraction of Derry.
