In summary it is down to the fact of the features of colourism in India manifesting in the American setting, and then creeping into Africa.
Let us consider the nature of colourism in three different parts of the world, Europe, Africa and Asia. In Asia. In the case of Africa I am referring to Sub-Saharan Africa and with Asia I am referring to Indian subcontinent in particular.
I focus on these three regions in particular on account of ther racial and ethnic homogeneity, although in India an allowance has to be made for caste differences.
In Europe let us consider the case of blondes vs brunettes. As the saying goes, "gentlemen prefer blondes, but marry brunettes". In Europe the preference for blondes is basically cosmetic. A blonde is considered prettier but not necessarily worthier.
In Africa too the same applies. A lighter skinned woman may be considered more physically attractive, but the ebony complexioned woman is not considered less worthy as a woman. Admittedly some changes appear to be occurring here where light skin is due to white Eurasian admixture. How much of is due to the proliferation of video vixens in hip-hop videos is nothing I can be sure of.
It is India is where the situation is entirely different. In India to be a dark-skinned woman is not just about being less beautiful, or ugly to all intents and purposes. It seems to be treated as the effect of a karmic sin, where her suitability as a wife, a mother and homemaker is open to question, where her worthiness as a female of the species is held in doubt.
It is expressed in cases examples like these:
The parents tell the friends of girl not to play with her on account of her complexion, in her presence (In truth this probably happens to boys as well)
A person outrightly declines, or relucts to make physical contact with a blood relative or an in-law on account of their dark complexion.
Girls are denied roles in school plays because they are the wrong complexion.
Strangers make direct disparaging comments to a girl, or make disparaging comments within earshot with the intention that she hears them. It as though the girl harbours or embodies an unwelcome spirit, or her body is the expression of an unwelcome ancestral feminine presence.
Female relatives and acquaintances express the sense of the girl being socially handicapped and wanting in some way, and offer all kinds of advice and treatments for the condition
A girl is told that her father and grandfather went into mourning for months when she was born with an Aquitaine red complexion.
For me parents and relatives who express such attitudes, or are even tolerant of such expressions within their social environment even though they don't express such attitudes themselves are being disloyal to their girls, regardless of how much they love and care for them. It as though no matter how much they love their girls, a deference or loyalty to some social or cultural beliefs and attitudes comes first. This for me is wholly unacceptable, and I express the sentiment irregardless of how much my opinions carry weight or are accepted within such communities.
I see this state of affairs as being rooted in the fact of Indians being biracial, with the light-skinned Indians being the whites and dark-skinned Indians being the blacks. So the colourism towards dark-skinned women in particular is really the hostility rooted in the era when the blacks and whites were separate. Having come together through miscegenation, that hostility is taken out against the darker-complexioned women who express those original differences in their complexion. This is irrespective of the fact that the genes for complexion are a minuscule portion of the whole human genome. I have the suspicion that an earlier generation of dark-skinned women may have been quite hostile to the miscegenation later and current generations suffering from the ensuing resentments.
For me this state of affairs is morally wrong because a community has a duty to motivate and inspire their offspring, both male and female to attain their full potential and this attitude is a betrayal of that duty on the most specious of grounds.
Among the African diaspora ie in the USA, I am beginning to see this shift away from colourism bound to perceptions of beauty, to one based on perceptions of a woman's fundamental worthiness as a woman simply on account of being black, the association with a karmic fault, and the ensuing effect on their self-esteem and even destructive behaviours which arise from those sentiments.
The current situation in America is more the result of the pressures being placed on a black community by a totally white controlled media and economic structure. India is not ruled by white people, so the colourism must be the result of a biracial or outwardly biracial power structure being disloyal to its own kind, its darker-skinned females in particular. It is either that a society which is riven by unthinking loyalty and attachment to old prejudices, or one in which some elements within a people who were forced together by practical need or unyielding cultural regulations still have at heart the original seeds of their hatreds, and continue to take out that on Black females.
For a community in which one expects to see a psychic unity, a psychic cohesion, this structural fault expressed in the oppression of women is unacceptable. The emergence of something like that within the American population, and the sense that something may develop Africa where there is hardly a population which may be regarded as biracial (Sudan being the exception) is the cause for this focus. It has to be dissected as much as possible for the faults within it to be seen, so societies which haven't gotten to that state can examine themselves better and check themselves from falling into that state.
I hope this short answer explains my reason well enough, and as I have mentioned earlier, caveats apply.