The first public academic to my knowledge to begin crystalizing the problem of private prisons and the prison industrial complex was Angela Davis [1] -- I first remember hearing her address this in a 1998 lecture at Northwestern.

Ruth Wilson [2,3] has worked for years analyzing and working to end the expansion and privatization of California's prisons, through both academic and grass roots efforts [4]. Her "Golden Gulag: Prisons, Surplus, Crisis, and Opposition in Globalizing California" [5] book is both accessible and rigorous, I highly recommend it. I am a bit shocked that their and foundational work were not mentioned in the piece.

There's a discussion between Davis and Wilson here [6] where they surface the mass incarceration/private prison issue, and detail the pathology of California's prison system.

[1]https://www.amazon.com/gp/product/1583225811/ref=dbs_a_def_r...

[2]https://www.nytimes.com/2019/04/17/magazine/prison-abolition...

[3] https://www.youtube.com/watch?v=sTPjC-7EDkc

[4] http://criticalresistance.org/

[5] https://www.amazon.com/Golden-Gulag-Opposition-Globalizing-C...

[6] https://www.youtube.com/watch?v=FGPVPrJGXsY