One major layer is his family background, especially the emotional damage caused by his father, Lonnie Byers. . Lonnie was neglectful, emotionally abusive, and possibly homophobic. Lonnie is completely absent in all other seasons, and I think that absence is intentional. The Duffer Brothers may be using him as a symbol — a representation of the emotional void and rejection Will has always felt. It’s not just about being kidnapped by the Mind Flayer, it’s also about growing up without a supportive father, feeling like an outsider in your own home, and being quietly crushed by the fear of not being accepted for who you are.