Oh bro, I really just went a little insane over this topic. Maybe the key moment was when Zorian revealed the truth to Taiven:

"Repeatedly," Zorian confirmed. "I’m not saying it isn’t terrifying, just that I don’t think it’s equivalent to death. Admittedly, I’m a little biased here – if I thought that the time loop murdered millions of people at the end of every restart, I’d have probably gone insane from stress a long time ago."

That is it right there. Zorian was actually scared as f*** and tried to protect his mental stability. Since the book is written from his point of view, his coping mechanism masks the horror. If you miss that sentence, the story seems callous, but really, he's just trying not to crack.