Steven Stone, to me, is a man who does not see his own value. Its not that he lacks self-worth or self-confidence, he just doesn't think he's all that. Steven has a lot of critics. Of course he does, he's rich and powerful. There's always people who are gonna say that he's nothing more than a spoiled nepo baby. But there is no bigger critic of Steven Stone than Steven Stone himself. In any given conversation, he'll be the first to ask "What's so great about this Steven guy, anyways?" Sure he's rich and powerful but what's the big deal? It doesn't make him better than anyone else. It's just a bunch of dead weight dragging him down.
He never wanted to be rich. He never wanted to be powerful. He's just a guy who likes rocks. If it was up to him, he'd be in some cave in a far off region studying rare rock formations. The only people who knew his name would be fellow geologists.
That's what makes him a great foil to Zinnia, I think. Zinnia is a woman for whom her responsibility is everything to her. Steven is a man who wants nothing more than to be freed of his responsibility.