The clown's impact on the children of the Derry series shapes them throughout their adult lives, transforming them into the very adults who keep the community's pattern of hatred ongoing. It finds easy targets on children from broken households — children who frequently mature to replicate the identical behaviors as their guardians. But, the Hanlon family distinguishes itself as a rare example of a households that remains intact, which may explain why Mike, even after electing to remain in the town, remains the only Loser who never fully falls under Pennywise's sway.
In the fourth installment of the series, Leroy Hanlon at last grows more aware of the paranormal entities surrounding the neighborhood, especially when the entity begins tormenting his son, Will Hanlon, during their angling excursion. The Hanlon clan comprises some of the few grown-ups who are aware that something is amiss with the municipality, especially Leroy, who was shown to be receptive to the Shining when he was capable of sensing Dick Hallorann's use of it in episode 3. Later, he spots one of the clown's trademark inflated orbs outside his house. This gift, coupled with his failure to feel fear, along with the foundation of his household, could be why he's able to see Pennywise's hauntings. However, consider if that psychic sensitivity is generational, and a key factor Mike is one of the only adults in Derry who resisted succumbing to the town's malevolence?
The boy is a member of the collective of children at his school being tormented by Pennywise. All his school friends hail from broken homes, with parents who refuse to accept they're being targeted. The reason Will is being pursued is due to the viciousness of the town, combined with his likely receptiveness to psychic abilities, which makes him susceptible. The Hanlons are fundamentally outsiders in the town during 1962, which lends itself towards the family sensing anomalies exist about the town from the beginning. Additionally, they possess a solid base that isn't fractured, in contrast to the folks who originate in the town, with bonds that have decayed within.
Drawing from the original book, we know the juvenile Will will end up at the Black Spot, where the psychic will rescue him from a blaze that the local KKK members of the community will cause. In the 2017 film, we observe that he has a son named Mike and that Will eventually perishes in a fire, with Leroy surviving his own son and taking his grandson in. The public account in the film is that Mike's parents were on substances, but now that we see him in the series, that's difficult to accept. Perhaps the shy youth, once he became an adult, leaned into drink to rid himself of the torments, or perhaps the corrupt town affected him initially, with the KKK ultimately finishing the job it began years ago. Be it via the terror of Pennywise or through the malice of the community, seeded by Pennywise, the creature in the end achieves the final victory on Will.
This chain of events would explain how the elder Hanlon changes so drastically from what we witness in the first film and Welcome to Derry. In his later years, Leroy appears resentful and much harsher with his discipline. Because he survived his own son, it's understandable to see such a drastic change. Nonetheless, his statements carry more weight now that we know he's seen Pennywise's hauntings and the impacts they had on his son. In the initial sequence of It, we observe Mike pause to use a stunning device on a animal at Leroy's farm. Leroy reprimands him for hesitating and provides an metaphor that results in a kill-or-be-killed scenario.
“There are two places you can be in this existence. You can be in the open like we are, or you can be trapped inside,” Leroy says as he points to the creature. “You dawdle hemming and hawing, and another is going to make that choice. Except you won't know it until you experience that bolt between your eyes.”
In hindsight, this could represent a bit of foreshadowing, something he regrets not imparting to his own child. Perhaps he desires he had done something in his past, but for some reason, he couldn't resist the repellent attraction of the town.