This is such a great question!!! I largely think that it has to do with a lack of representation and historical and injustice. Many of the men that completed the feat did significant parts of it solo. There is still an outdated narrative that solo travel for women can be dangerous, in particular when traveling off the beaten path, and I cannot debunk this enough! I have traveled to nearly 80 countries solo and I've not felt unsafe in any of them. The places I've felt the least safe while traveling are the United States and Paris. That's why I love that this platform shines a light on so many female explorers so that women see it is possible and safe to explore the world on your own terms.
With regard to black people, for centuries, the movement of black people has been severely limited by white supremacy. Whether you think about colonial times in Africa, South America and the Caribbean, or Jim Crow in the US, or apartheid South Africa we've seen laws that were put in place to limit our movements all over the world. Beyond that there is a severe economic disparity between black people and white people because of history. Couple this with a lack of representation and people feeling like certain things aren't for them and you have a lack of black people who have extensively traveled in modern time, as compared to their white counterparts.
Don't get me wrong, African/black explorers have explored the world for centuries! We can look to Matthew Henson, or many black American entertainers who in the 40s, 50s, and 60s preferred traveling and living abroad to being in the US, and others that were breaking barriers years ago. I hope that my journey inspires more black people and people of color in general to explore more of the world.