Treason is the actual charge with which the FBI intended to charge Hillary Clinton.
The FBI never intended to charge Hillary Clinton with treason. If they had, they would have recommended exactly that. They didn't even intend to charge her with mishandling classified information. If they had, they would have done so as well. The only thing that happened was that in deciding that she had done nothing worth an indictment over, Director Comey decided to violate protocol and offer critiques about her email practices. Presumably because he was Ken Starr's right hand man all during the 1990s, trying to pin something - anything - on the Clintons. And failed. Because they hadn't done anything illegal then, either. (With the exception of Bill lying under oath about an affair in a nuisance lawsuit.)