Literally stealing billions of dollars doesn't seem that bad to you? If my almost-worth-16-billion-dollars company was failing, I would do a lot to save it, but that would never, ever include stealing other people's money, nor defrauding anyone, nor lying about anything. Which, of course, is why I'm unlikely to ever have a company worth nearly that much.
What you're really saying is: "If you were a narcissistic compulsive liar who was defrauding thousands of people and your lies began to untangle, you would dig yourself in deeper and deeper with more and more unrealistic lies until the whole thing collapsed. It happens all the time." Yes, that seems to be what happens to compulsive liars, and prison is absolutely appropriate for these people (when it results in this level of damages). The same behavior in 2008 also should have resulted in prison time. It did for one person, and probably should have for a lot more.