Great analysis by Benjamin Lessing on the Monkey Cage:
Brazil’s prison gangs wield immense power on the streets, and driving the violence is a dynamic of competitive expansion. After dominating and transforming the criminal underworlds of their respective home states in the 1990s, the PCC and the CV are now colonizing prisons, urban peripheries and trafficking corridors throughout the country. The scramble for Brazil’s criminal markets is on.
[…]
Street criminals can have many reasons to obey prison-gang rules. The most important is probably the one a Rio trafficker gave me: “Whatever you do on the outside, you have to answer for on the inside.” Moreover, the likelier you are to go to prison, the stronger your incentives to stay friendly with the gang that runs the place. This means that higher incarceration rates and anti-gang crackdowns can actually increase prison gangs’ influence over street-level actors (as I argue in this Monkey Cage post and a forthcoming paper).
This influence, David Skarbek shows, allows prison gangs in Southern California to govern otherwise unruly and violent urban drug markets, increasing overall profits and taxing the surplus. Indeed, from Los Angeles to Rio, prison gangs’ projection of power has transformed retail drug markets. These are usually fragmented, because it is difficult for one organization to control much turf. Mass incarceration solves this elegantly, arresting street criminals and physically confining them where prison gangs can easily reward obedience and punish defection.
[…]
The CV originally spread when officials unwisely dispersed its leaders among Rio’s prisons. PCC leaders have also been transferred to or arrested in other states, where they invariably founded local chapters. Conversely, some local copycat prison gangs were founded by inmates who spent time in PCC-controlled prisons in São Paulo.
It is probably better than most articles published about the massacres in Brazilian media. (I say “probably” because I admit I have not been following the coverage thoroughly.)