Answer // Explanation:
The main reason is the media and how they present the action to the people. Also is important to notice against who is the whistleblowers
While Snowden was presented as a robbery of crucial information for the safety of the U.S
The other cases were represented as angels against the corporate demon (Enron and Worldcom)
US citizens may have seen good that someone spoke the truth about how big the company's lie and the government was grateful as it influences for further intervention and legislation on big company's.
For Snowden there were no winners, the media and government see their images decay so they needed to attack the person and their belief rather than justify why they need their information about everything the citizen do.