Why do prominent public figures resign, instead of being prosecuted, when they appear to have committed a crime?

Question

A few examples:

• Iceland's prime minister resigned when his relationship to the Panama Papers was discovered.
• The police superintendent in Chicago, Illinois, USA was fired when a video containing a police shooting was uncovered more than a year after the shooting took place.
• A regional administrator of the US Environmental Protection Agency resigned after dangerous levels of lead were found in the area that the administrator oversaw.

These acts prompted suspicions of money laundering and cover-ups, and gross negligence. Why are these public figures typically fired, or "voluntarily resign," instead of being prosecuted for crimes that they could plausibly be accused of? Is it a case of the law not being applied to the powerful and well-connected, or are there other legal reasons?

Answer 1

I will address only the legal issues.

Prosecutors for very good public policy reasons are not required to prosecute every crime they have suspicions about.

When exercising this discretion they consider:

1. Is the act, in fact, criminal - many of the things you list, while reprehensible, unethical, and possibly immoral are not actually criminal.
2. Do they have the resources (time, staff, money) to collect the evidence and run this case as opposed to the thousands of other crimes out there. There are always more crimes than can be prosecuted and these have to be prioritised in some way.
3. Do they have enough evidence to gain a conviction beyond reasonable doubt. People can be fired or resign on suspicion, they can't be convicted on it.

Answer 2

This interview with the man who served as the lead prosecutor on the Enron Task Force clarifies some of my questions. In essence, as one of the other answers mentioned, just because someone committed a careless/immoral/negligent act doesn't make it criminal according to the law. And establishing that there was actual malice and intent to deceive, which could be more clearly categorized as criminal, is difficult to prove in large organizations where there is no one clear bad actor.