You're asking a pretty big question because it deals with race relations and the way that the city of Los Angeles developed in part as a response to those relations.

The Death of Latasha Harlins is something that was thought to be a contributing factor. A Korean grocery owner believed Latasha Harlins was stealing some OJ. She tried to stop her, a scuffle ensued and then Harlins tried to leave. Du (the owner) got a gun and shot Harlins in the back (and the head).

She was found guilty of voluntary manslaughter which carried a max of 16 years in prison but the judge gave her 5 years of probation, 400 hours community service and a $500 fine.

It was seen as one of many double standards when it came to meting out justice. The King verdict was yet another slight to the African-American community.

You're also dealing with a region in Los Angeles that has had an incredibly complex relationship with that community from the time that the major migrations from the South occured. You have housing covenants which forbid certain homes to be sold to blacks or anyone of color. You have a history of rioting going back to the Watt's Riots in 1965 and people in the community who experienced them still being alive in 1992. Then you have the influence of the Black Panthers and the subsequent efforts by the FBI to undermine the Black Panthers and other groups for being subversive. Gang culture creeps in and changes whole communities. There's the effect that crack has on the community. That drastically changes the relationship many black communities have with law enforcement (and this is a development that has being going on for years before crack).

There are a lot of complicated socio-economic and racial issues that served as kindling for the riots and you could really take at least one course simply on Race in LA (as I did) to understand why the 1992 riots happened at all. I really gave huge broad brushstrokes because you're asking about something that spans the better part of 50 years but the point is that Los Angeles and the Black community have had a simmering and sometimes boiling tension for years and years by the 1992 riots.

This is mostly from memory but I remember one good source of info on the growth of LA and how various forces, races and interests molded the city (and thus how these forces might have impacted the black community in 1992) is City of Quartz by Mike Davis

There were a lot of simmering tensions in LA at the time of the riots. There were a lot of simmering tensions across the USA at the time of the riots. But they need never have boiled over into full-on riots--they didn't resulted in riots in other areas of the country. So saying that the tensions were building towards a boiling point anyway is to provide an inevitability to the riots that was simply not there. There were no riots when the Rodney King tape first came out, even though people were really angry and upset about it. There were no riots during the trial. There were no riots after the Latasha Harlins verdict. People were controlled and expressed their anger and search for justice verbally and in print. Sure, there was a lot of anger--basically every black person I knew in LA, from janitor to doctor, had been stopped by the police for "driving while black" or "walking while black". In other words, for existing. For being black and being in a nice neighborhood. That sort of situation. And there had been a lot of complaints but no change. When the Rodney King trial happened, people put their trust in justice, not rioting. If you go back and read newspaper archives of the time, you'll see that people were controlled in their anger. They believed that now that this tape existed, which showed an unresisting black man being viciously beaten by police, the police would be punished. When that didn't happen, then some people began expressing their anger in a violent way. But keep in mind, it wasn't "the black community" as a group that was rioting. There were some people who were rioting due to anger at this socio-political situation, and then there were a lot of others who were piggybacking on the riots to loot because they wanted to loot. Once you start to have a situation spiraling out of control, it has a way of self-perpetuating for reasons that were unrelated to the reason it started.