Because nobody cared.
No consequences, profit-driven company, metric-driven agencies, nobody cared.
Constructing a modern-day criminal justice system from the ashes of the Bad Old Days is going to be a project for our generation or the next or the next after that, but it probably requires burning things to the ground.
In the meantime: Most of the liberal democratic ideals you and I were raised on with regard to criminal justice were from academia musing on what should be, or from copaganda television shows lying about what is. They live in our heads - if you want them to be real, you have to make them real.