The standard rumor at the time was that Rumsfeld, as chief of staff, had persuaded President Ford to appoint George H.W. Bush as director of Central Intelligence, assuming that that got rid of a potential competitor for the presidency.
Another factor is the decision, made in 1976, to sharply divide the FBI and the foreign intelligence agencies. The FBI would collect within the United States the foreign intelligence agencies would collect overseas.
You want to keep intelligence separate from policy.