r-selected people thrive by leeching off their culture, using the resources produced by others in their culture to subsist and to spread their seed. But this strategy of leeching only works if there is something to be leeched. That is, r-strategists can only thrive in a successful culture. So it would make sense for women to want not just r-strategists, but r-strategists from a successful culture.
Keeping this in mind, it makes sense that women are most attracted to r-selected white guys. Because white culture is the wealthiest and most successful culture, and therefore an r-selected white guy who lives in a white society is living in paradise, since there is so much wealth for him to leech. Black Americans, even if they are on average more r-selected than whites, are less desired than whites, because even though black Americans are sort of members of American society, and in the present day have just as much privilege to leech off welfare as whites, they aren't really fully integrated past the point of no return. For example, it is conceivable that a white nationalist movement will rise and the whites will separate from the blacks, and take the wealth with them. Then r-selected black people will be like parasites without a host. But r-selected white people will always always have a host for as long as white society continues to live.
This also explains the extreme repulsion American women have to Indian men. Because on one hand Indians are an impoverished culture. But on the other, the Indians who are in the USA are on average very successful and educated people. This is the exact inverse of what women want. Women want an r-selected man from a successful culture. So if you instead present them the opposite, a K-selected man from a destitute culture, they should find this revolting.