Well, let me see if I can break it all down, and please, anyone, feel free to correct me, or add your insights.
All my life, I have been powerfully attracted to white females. Thankfully, as a black man living in this extremely racist nation, I never lived in a place or time when this attraction, if detected, could have gotten me killed. I believe it's a fact that, due to white dominance, most have been programmed to accept the dominant race's standard of beauty. In a recent documentary on the tragic and horrifying history of sports legend O.J. Simpson, one of his former business associates let slip a remark meant as a compliment, but it revealed the man's bigotry. He said that Simpson was a very handsome guy-- for a black man. He explained that he almost has white features.
When black female celebrities like Jayne Kennedy, Alicia Keys, Lisa Bonet, Halle Berry, Meghan Markle, and others are fawned over due to their interracial beauty, this is largely attributed to the white standard of beauty.
I admit, I totally succumbed to the programming from a very early age. I Dream of Jeannie, Bewitched, The Brady Bunch, Gilligan's Island, Marilyn Monroe, Lynda Carter's Wonder Woman, Charlie's Angels, Daisy Duke, Heather Locklear, on and on... Yes, beautiful white women are the standard, and I was always most aroused by blue-eyed blondes, blue-eyed brunettes, and green-eyed redheads. I lust after many beautiful women outside my race for the wonderful contrast, the aforementioned programmed beauty standard, and for the inescapable racial taboo. But it's the white girls...
That last element plays a very big role, I believe, in the cuckold/hotwife fetish, although most prefer to ignore it. Can it only be about the larger endowment of the black penis? This is another racial stereotype, by the way. Bigger dicks have nothing to do with the taboo aspect everyone talks about. Throwing off the blanket to see exactly what it's about, we have to acknowledge the underlying racial dynamic. I love fucking white women because I'm not supposed to. And even more, I love fucking a married white woman because I'm really not supposed to, since she's married, and white. Of all the unobtainable white females, it is the lawfully-wedded white female who is supremely off-limits. And in this kinky lifestyle, that makes the attractive white wife the most desirable. If all black men had average-sized dicks, would white wives still want to be fucked by them? I'd say that the numbers might come down a bit, even substantially. But I believe a good proportion of them would. And that would be because of the racial taboo which amplifies the pleasure on the psychological level. In role-play, the slaveowner/slave sex fantasy is quite popular. And that's not restricted to black dick size. But the fantasy is indeed a huge turn-on. I've experienced it once, though the couple played it off very subtly.