Maybe blacks suffer crime more, but that has always been the case. I think the quick turnaround comes from the media infatuation with white cops shooting blacks. This has totally backfired on the liberals as more and more black people realize that heavily militarized government has to be countered. This was the original intent of the bill of rights.
I think it comes from the spread of the CCW laws, and of open carry demonstrations around the nation.
Both of these have been heavily publicized (in opposition by the old media and elites) but what that has done is inform many black people that they can legally have a gun and it is their right. Heller and McDonald had a lot to do with it as well.
Man urban black people simply assumed that their right to bear arms would not be acknowledged by the courts. As they learn that is not the case, the attitude has changed.