David Bedford announced last week that he was going immediately. Sarkis had been given a pay-off and left the previous week.
Third Sector has learnt that Bedford would have faced a vote of no confidence by the trustees if he had not resigned.
The trustees were told early this year that Bedford had concerns about Sarkis's performance and would be instigating a review, but it is understood he declined to give more details to the board.
Sarkis then lodged a grievance against Bedford, vice-chair Linda Sharpe and treasurer Chris Poulard, but the remaining trustees were not told what her complaint was.
The charity initially made an offer of a £40,000 golden handshake to Sarkis, equivalent to six months' pay.
A statement handed to delegates at the YMCA's annual conference two weeks ago said Sarkis, who was due to speak, had left the organisation. No further announcement or discussion about her departure took place at the three-day event.
Trustees were told last week that Bedford had resigned with immediate effect. The charity decided against a public announcement of either departure.
A YMCA spokesman said: "We would like to extend our thanks to Angela for the contribution she has made to the YMCA movement and we wish her continued success in her future career."
He said Bedford believed it was the right time to stand down: "He is conscious of the opportunity for YMCA England to move into a new and exciting era, and feels that a new chair can help to recruit a new national secretary and form a partnership to take the organisation forward."
He declined to answer further questions. Neither Bedford nor Sarkis was available for comment.
The YMCA calls itself "a leading Christian charity committed to supporting all young people, particularly in times of need".