Seems to be a bit of a difference in how netorare is handled between the east and west in general. In the west it's just cucking, in the east it can be cucking or more an in depth exploration of the destruction of something pure or beautiful. I've seen a few (very few) examples of this from the west, but over all that's how it falls out. Sure, it came from the east, but those of us in the west have done what we always do in these cases and ruined it.
Well, cuckoldry has been a genre before the term NTR seeped into the western coomer community. It just kinda merged into one in the west, but the cuckoldry basis still has a strong influence. And many western devs just assume NTR is the same thing with a different name. It's not so much a ruining a genre taken from Japan, but kinda just taking the name and applying it to whatever they were doing before.
As for why western side developed the predominance of cuckold stories while Japan developed the more corruption focused netorare, I could make a conjecture. Individualism, feminism, civil rights... things like that are concepts that are more ingrained in western society. On the other hand, Japan values conformity and lags behind on those social issues by a couple decades.
The average western porn is gonna depict strong women who has all the agency, while Japanese AVs are much more likely to feature a passive women who is the subject of whatever sexual harassment come their way from ugly bastards. So it makes sense that western NTR, aka cuckoldry, will feature strong women who wants to humiliate the husband, and that humiliation becomes the main attraction. Japanese NTR is less often focusing on that aspect and explores the corruption of the women in detail.
I ain't no porn historian and made all that shit up, though. I just think western cuckoldry tend to give off some gay vibes with all the chastiy cage, bull busting, sissification, and the dude licking up cum. I ain't watching porn to see some cuck get tortured. Give me the corruption arcs of the women in Japanese NTR, thank you.