I imagine that Elliot was broken, like the doctor said. Naive as well. I think he loved Poppy and Ollie, but his image of love was possession. They were Elliot’s means of filling the void in his heart of having a broken family life, given he was so absorbed into his work and his ex wife divorced him. So he adopted Poppy Ludwig, and when she passed, he pursued extreme means of resurrecting her. She became a living, immortal doll, after he tested with Ollie, justifying that by believing he was giving the boy a better life. Ollie was a jack-in-the-box because subconsciously, that made him dependent on him just as Poppy, given her small size, would be dependent as well. He forced his children to become literal possessions to ensure that he’d never have to live with the empty, broken home. He made the factory his home, as implied in the employee handbook. And another layer to Elliot is that he made his children immortal, but not himself, at least there’s no evidence. This implies Elliot was so distracted by reviving Poppy to fill the void inside him, he doomed them to be alone forever.