A big part of this has to do with drug crime and how it impacts black neighborhoods vs. white neighborhoods. The shorthand version is that black neighborhoods generally have "corners" while white neighborhoods have "dealers".

Dealers are discreet. You come to them, or they come to you. The transaction generally takes place indoors, or at least on private property, as does the drug use itself.

Corners are not discreet. Drug sales are conducted out in the open, in public. Drug use often happens nearby in public, as well. This has repercussions. Open-air drug markets attract prostitution, robberies, assaults, and the like. And corners become lucrative real estate in black neighborhoods. Gangs will fight over who gets to sell at a corner.

Of course, if you're an ordinary citizen, their drug corner is just your neighborhood, so the residents will pressure police to get the most violent offenders off the the streets. Prosecutors and police both understand this dynamic, and prosecutors will push for maximum sentences for specific individuals arrested for drug crimes near contested corners, in order to keep them off the streets, and keep violence down.

This is often called "enhanced prosecution", and you can read a decent introduction to it here. This article is about policing and prosecutorial practice during the years Vox's study covers, 2011-2016. Of course, in a post-Floyd world, this is all very controversial again, and one of the reasons you see violent crime numbers trending up.

In short, blacks who use drugs are more likely to buy, sell, and use them in public, which leads to gun violence and other assorted problems in the neighborhood. This is why they get arrested more, and why some have received higher sentences. Black drug crimes create more neighborhood consequences than white drug crimes.