Prosecutors can and do pierce the corporate veil [1]. Otherwise, losing money on their investment seems like fitting punishment for disinterested shareholders.
[1] https://en.wikipedia.org/wiki/Piercing_the_corporate_veil
No one pushed a super-educated and super rich CEO to do anything. His greed did. Shareholders that sold got lucky, those that didn't are paying the price with tens of billions in penalties.
Jail CEOs and a lot of problems will be solved.
If your 401k invested in VW - which is very likely - are you also supporting its criminal activity?
That is to say, if mutual funds (which your 401k likely comprises) stand to lose significantly to unethical behavior, then they will be a LOT more choosy about who to invest in.
Your argument to the extreme about jailing parents/teachers is missing my discussion point.
It's not deterministic but it does create a positive feedback loop of ethics compliance.
They are paid millions to do this and they are free to leave the company or switch career.