Honestly, I don't think he does believe the women consented clearly and enthusiastically.
I think he pretended to believe that, to the women, because it enabled him to minimise what he'd done to them - and groom them into further degrading sexual acts. He could pretend it was all fine and normal and play dumb, and then pretend to be shocked and hurt, and even play the victim, with them if they ever pushed back. I think the crossing of boundaries and infliction of pain was something he found specifically arousing, so the idea that he didn't know he was doing it doesn't fly with me. Maybe in the very, very days, when he was pushing boundaries with his first victims, he could convince himself it was all a game or "it wasn't that bad". Or whatever. But by the 2000s it seems clear lack of consent was a feature for him in his sexual encounters, not a bug. He got off on it.
And now he's lying his head off, trying to make it all look like an innocent bit of autistic miscommunication, or a sex game that went a bit too far. I've seen a few conversations spring up here and there about what consent really means, and what Gaiman's concept of his own actions may have been. But to me, those conversations are all irrelevant to this case. In all the scenarios we've been presented with, Gaiman knew what he was doing. His "but I thought they were into it, I swear!" act is just an attempt to create some ambiguity. To do damage control.
The truth is he chose his victims because he knew he could push past their boundaries. He leaned on whatever pressure point he could find, and played whatever role suited him in the moment, to get what he wanted. It was all calculated. His M.O seems to have been to set his sights on a vulnerable woman, test her boundaries, push past them, and then play monster or charmer (or both by turns) to keep her in check. I just don't buy that he was unaware of what he was doing, or could be unaware now. It's just a self-preserving lie.