The financial incentives are set up to produce as many dangerous criminals as possible. Without repeat offenders, many private prisons would have to close.
The solution is simple: The US should actually ban slavery and should also ban private prisons.
It should replace private prisons with ones that are rewarded when their former prisoners become productive members of society.
There should also be a cap on the ratio of prison spending to education, mental health, and community service programs.
The rest of the inmates are in prisons that are state-owned and thus inherently nonprofit, and the guards & other staff are either state or federal workers. Contractors do things like provide commissary goods or run the inmate telephone system, but the guard in the tower at your local prison is a state employee.
Although there's also the factor of better social safety nets as well, which will play a large part.