Now here's something interesting and weird.
I saw some studies a few years ago that said that the cuckold gets excited seeing the wife being fucked because the man is the genetic donor for the woman, the woman will receive the man's genetic material and mix it with hers to have a child, and you love your woman is that you recognize her as a perfect genetic match, and see another guy fucking her (sex is the no compromise exercise for procreation lol)
it's seeing someone else competing with you and wanting to end your inheritance, and instinctively you get excited that no matter how much the guy fills your wife, you want to put your "your seeds to swim together" and I think in interracial this is more evident because of the differences.
I don't know, for me it's crazy, I don't even remember where I saw these materials, but it explains why a lot of cuckolds , including me, get excited at the idea of the bull getting his wife pregnant!