Why did the Trayvon Martin case become such a huge national story?

Is it because an innocent black teenager lost his life at the hands of a man, George Zimmerman, who “racially profiled” him? Is it that the victim is black and the shooter was not? Is it because the major media push the narrative that white anti-black racism remains an “unresolved” national issue? Is it because “civil rights activist” and MSNBC host Al Sharpton demands the shooter’s arrest, threatening peaceful civil disobedience and “economic sanctions”?