Rural areas are poorer than cities, yet cities have the majority of crime and a significantly higher crime rate than rural areas.
Personally I think it has to do with the whole gang culture movement. A logical person would think glorifying being in a gang/drug dealing/going to prison/'hustling' may lead to higher increases in crime. Most rappers have to have 'street cred', i.e. be part of a gang, committed murders, etc. In a normal society, these things are universally frowned upon, while in inner city communities they are lauded by too many.
Also the people saying "it was lower than in the 90's" or "its only 6.7 lol" are coping hard. First of all, the increase we've seen in murders is the biggest increase ever. Secondly, murders aren't the only crime, the increase in murders correlate to the increase in robberies, assaults, rapes, vandalization, etc. On top of that, America's murder rate is higher than places that are dirt poor, have an active war in their country, etc.