For a number of years, Congress has spent an inordinate amount of time and money in repeated investigations in regards to former Secretary of State Hillary Clinton and her emails, the use of a private email server, and the deletion of emails that may or may not have been considered classified.
On more than one occasion it has been revealed by individual members of the various committees that all of these investigations have been one form of political grandstanding or another with the deliberate intent of sabotaging Madam Secretary's credibility as a presidential candidate.
Should the president issue a full pardon to Madam Secretary, Congress would be unable to further pursue this matter, eliminating the government waste involved in pursuing it further.