>>48690855We're never outright told, but his grandparents and old neighbors indicate that he was a quiet and anti-social boy who always worked better with machines than with other kids. They also make it clear that his parents were neglectful at best and possibly abusive towards him. So he grew up with the people responsible for loving and raising him treating him coldly and being either unable or unwilling to teach him how to actually interact with his peers. He's well-spoken and clearly capable of being charismatic to at least dumbasses, but he never really learned how to connect with others, and his parents probably actively discouraged it.
Then Platinum and USUM show his relationship with Rotom. That shows that while he was unable to connect with others, he clearly WANTED to when he was younger. He went the whole nine miles and created means for Rotom to gain new bodies that it could use to physically interact with others and wanted to play with it. USUM also has him speak much more warmly to the Rotomdex Rotom than he does or has to anyone else in the series, and even promises to respect the little bugger's wishes and leave Alola alone.
It's just very likely that Cyrus was just a smart but neglected and lonely boy who hated what he viewed as the weakness in himself and the cruelty of others like his parents and just decided that the idea world would be a world without emotion or longing or spirit. To be fair, even nice people like Cynthia are pretty harsh to him and don't actually try to understand him, even if their reasons for viewing him negatively are understandable.
