Butterfield was a minor White House scheduler or some such. He had been put in charge of setting up the taping system of The Oval Office when in 1972 Nixon decided to record all conversations made there. Butterfield later wanted to quit because he thought Nixon was a boob but Nixon appointed him head of The FAA months before the Watergate Hearings. So Butterfield was gone from the White House. John Dean flipped and testified for many days telling all about the "Nixon White House Horrors" without knowing....for certain... of any taping system. Nixon's people were screaming LIAR, LIAR about him constantly. Butterfield knew about the taping system. Come forward? Nope.
Dean apparently said he thought there might be recordings made in The Oval Office so committee investigators started pulling in White House employees, swearing them in and questioning them behind closed doors. They question Butterfield and .... Bingo. Even then Butterfield asked not to have to testify.
"As soon as he revealed this to the committee staffers, he asked them not to call him to publicly testify. .....To reveal the existence of the tapes would be a threat to national security, he told them."
BTW, Nixon's people were constantly trying to withhold info based on.... National Security.
So Butterfield was no hero and he did not ever ..."Come Forward." He just testified when subpoenaed.
As soon as it was revealed there was a tape system the next question was.... who is the liar? John Wesley Dean III or Richard Nixon. Tapes revealed Dean's testimony was incredibly accurate.
And that, boys and girls, was the end of the affair.