Gender inequality in intermarriage exists in all communities of color in the Americas. From the very beginning, there were many more unions between European men and indigenous women than the reverse. Initially, this was due to the fact that most Europeans in the Americas were male. But later, as more European women arrived, the gender inequality did not lessen because Indian man-white woman unions were not given the same acceptance as European man-Indian woman unions. A white woman had to pay a high price in punishment or expulsion from her community for coupling with an Indian, while the same was not exacted from her male counterpart.
This gender inequality in interracial coupling between white and non-white extended to all people of color. European men who coupled with African women, whether briefly or for life, by force or consent, were almost never punished nearly as harshly as European women who coupled with black men. In fact, the ability of European men to "take" African women without "giving" their women to African men reflected and reinforced the white-dominant power structure the same way the gender imbalance in white-native unions did.
But that was the past. Today we see the reverse - there are far more black men with white women than white men with black women. What happened?
The interesting thing is the old trend of white men marrying non-white women in greater numbers than non-white men marrying white women did not reverse itself for any other ethnic group. Native American women/white man unions continue to outnumber white woman/Native American man unions, with a large percentage of the offspring identifying as white. Among the 'newer' immigrant or annexed/conquered groups like the Mexicans, the Asians and the Pacific Islanders, the trend is the same. More women of color marry white men than the reverse.
So why is there this reversal for blacks alone? My opinion is: it is a "reaction" to the Jim Crow era where black men could be lynched for even whistling at a white woman. Although whites oppressed all men of color, no other group suffered the extreme brutality the black men were put through. White women were always forbidden to black men,
In the light of this history, it is not surprising that some black men today see white women as the ultimate prize, a sign that they had "made it" in a white world. Others saw taking a white wife as a way of evening the score with white society which had denied the black man virtually everything else. This "prize" mentality is not unique for black Americans. It occurs in other oppressed peoples who live with their oppressors. Individual Israeli Arab men have expressed the view that marrying an Israeli Jewish woman was the only way in which they could "compete" with Israeli Jewish men, who were favored by society in virtually all ways.
Another factor, I believe, is the Eurocentric concepts of beauty that black men, and also women hold. This mentality is not new among black men. During the slavery era, blacks were already being indoctrinated into thinking that whites are superior in every way, including physical attractiveness.
After the civil rights movement gained momentum and it became less fatal for black men to be with white woman, many availed themselves of the opportunity, so their preference was able to translate into real numbers - an increase in black-man/white-woman couples.