I see it as a direct continuation of:

Slavery->Sharecropping and Jim Crow->mass incarceration

Slavery never ended. The name just changed to be more polite, with a fig leaf of freedom and free will. Additionally we realized two things:

1. It’s more economical to hold slaves in large central facilities than dispersed.

2. The best way to fight abolitionism is to convince the populace that the slaves deserve it.