"An attorney for the government may also disclose any grand-jury matter involving, within the United States or elsewhere, a threat of attack or other grave hostile acts of a foreign power or its agent, a threat of domestic or international sabotage or terrorism, or clandestine intelligence gathering"
russia committed a hostile act towards our country by trying to interfere with our election.
https://www.law.cornell.edu/rules/frcrmp/rule_6