Viewers seem confused: Nate seems like a totally different person now. They don’t love to hate him. They just see him as a loser. The writers hoped we’d suspend disbelief since we barely knew Nate before, aside from his medical background. He wasn’t fleshed out at all. Generally good guy on the surface. He was kind of a cad, yes, but his affairs were very plot-driven. In his story with Amanda/Elena/Devon, he was the only character that lacked a real POV.
Certainly, having Olivia return in some capacity would have helped us understand Nate more, perhaps giving us insight on his treatment of women and his identity as a physician, but I feel like we’re giving more thought to Nate as a character than the writers do.
Maybe if they’d deepened the friendship between Ashland and Nate, making Ashland more of a business mentor and a bad influence on Nate, it would have done a lot of the work to explain his shift, in addition to the anger he felt toward Devon over his career-ending hand injury. Or Imani as his Lady Macbeth goading him to more and more devious acts would have helped. But it feels like these shows are written week to week instead of planned out, and promising stories get dumped on a dime.
Nate as a big exec at Newman Enterprises just isn’t credible, and since he’s so opaque and ill-defined as a character, the audience doesn’t have anything to hold onto with him. These writers don’t want to (or aren’t allowed to) do the work.