I sort of disagree. It should be tackled from both sides. Shareholders do have some culpability for investing in unethical businessed and not doing enough due diligence. Your average person saving for retirement probably did nothing wrong, dumped the money in an ETF or IRA or 401k and the investment company handled it, but the investment company should have been looking at business practices and not solely stock performance.
Jail time for the decision makers. We already have a way to punish shareholders: Fines on the company. They should just stop being small fines and start at the very least exceeding the amount the company made through crime.
Jailing the decision makers will discourage crime to some extent. The temptation will still be there to pump numbers and make a lot of money. Hitting investors and investment firms in the wallet will encourage a culture of giving a shit about where you’re putting your money.