In summary: The theory is that from the mid 70s to the early 90s the prison population increased due to a real increase in crime, but after that, it increased due to prosecutors doubling the percentage of arrestees that they charge with a felony.

I wonder if the simple explanation is that over decades the size of the prosecutorial bureaucracy increased to deal with an actual increased work load, but after that work load started to go down naturally, that bureaucracy had to find a way to keep itself in business, and that was by charging arrestees who would have been previously released.

A DA's office where people are sitting on their hands is an office that will see budget cuts and staff reductions. We know from both government and the private industry that almost no department will voluntarily take a budget or staff cut, even if it is warranted.

Maybe we should try reducing the DA's budgets in some states/counties and see what happens to crime and incarceration rates.