They know he knowingly defrauded millions of people out of billions of dollars. If I did that, my mom would let me go to prison for the rest of my life because she knows she taught me morals and that human beings are more important than money and if I decide to ignore that moral framework as an adult then that's on me. Dude is an adult with a fully formed brain. Stopping a twelve year old from burning themselves on a hot stove is one thing, but if your fully adult son still needs to told not to touch the hot stove, it's time to let them fuck around and find out themselves.

That all assumes they had no idea what was going on, which I don't know is believable.

- You can balance their welfare vs. other goods, e.g. justice, well-functioning society, etc.

- Your view of their welfare can include their character, maturity, empathy, and taking responsibility for their actions. It sucks if that requires 20 years in prison, but that may be preferable to helping them be a free but terrible person for the rest of their life.