I doubt Bush specifically asked to have the 'Plame leak' investigated.
What the President did want to have investigated were the incessant national security leaks coming from the CIA and the State Department that went to the NY Times and Washingtion Post.
Go back and read the record. FBI was already investigating but he wanted a special prosecutor. He was tired of all the accusations being thrown at his administration over leaking the Plame identity for revenge that he asked Fitzgerald to investigate and he required all his wife house staff to answer any and all questions truthfully.