You switched from passive voice "Her story was elevated" to the active voice "Who in Duncan's community elevated his story?" This raises a question of fact - who got Breonna Taylor's story heard? How did they do it? Did someone attempt to share Duncan's story, and get rejected? Why?
It's easy to speculate. For example, Duncan didn't fit the racial narrative the media is comfortable with. This framing achieves several goals that the more accurate narrative, that police violence is evidence of severe problems with our justice system. The racial narrative pleases left-leaning viewers, it also plays better to right-leaning viewers because the problem of individual racism is still big, but much smaller and easier to accept. Or, they can love to hate the story.
A general failure of the American justice system is just not a narrative anyone wants to hear; it's too big. That narrative is one that challenges the mainstream view that the police are the good guys, and that American justice is fair. It's like "climate change", as a subject - much easier to pick it apart into anecdotes and pass judgement on individuals, which feels good and has no effect, or ignore it entirely, rather than confront the true scope of the issue.
Ultimately the problem is that "news" has shifted firmly from a "public service" of broadcasters, that loses money, to a for-profit endeavor chasing audience, aka "content". The former service tells us what we need to hear, but the latter only tells us what we want to hear. And precious few of us want to hear the truth, especially about ourselves.