I think you are about to open up a can of worms with this one. I get exactly what you're saying. IMO, for like the last 20-25 years or so, what would commonly be considered "urban" or "black" music has been used as a vehicle to set trends. If we look back to the civil rights era, there are documentaries out now that prove that there was a politically motivated agenda to demonize the leaders who stood for black empowerment. In turn, i think those individuals in charge of that campaign realized the influence of music as well and eventually moved to control it was well.
When hip hop music noticeably became the most popular genre, i think there was a concerted effort to change the narrative of the message in the music. Gil Scott Heron, Public Enemy, Poor Righteous Teachers, KRS-1, many others became the exception instead of the rule. Personally, i think that was by design.
Before we had the ease of access we do now, the radio played a major part in exposure. Because those types of artists stopped getting the push of the label in an era when they dictated 90% of what became popular, it was easy to put the spotlight to artists that focused on the negative aspects of the culture. And it worked...
It carried over for almost 3 decades. And here we are.