No he was prosecuted because he admitted that he knew that taking the pics was illegal. He knowingly broke the law. He also obstructed justice by lying to investigators. Clinton never lied to investigators and the FBI deemed that she did not knowingly expose classified information. You can say that the FBI didn't investigate her properly but you are about to read in the IG report that the FBI actually went too far with their investigation of Clinton, which blows a major hole in the whole Deep State conspiracy theory that Trump and his minions have maintained.