Keane was appointed successor to Jim Magilton at Portman Road on Thursday as he returned to football four months after quitting the Stadium of Light.
The ex-Manchester United captain's decision to quit the Black Cats last December came as a shock to the Premier League.
But Keane has now confirmed that he knew it was time to leave Wearside following a breakdown in trust with chairman Niall Quinn and majority shareholder Ellis Short.
"One of the big conditions I had when I went to Sunderland was that there would be no interference with team affairs," said Keane at his first press conference.
"But when someone tries to move the goalposts, it is nothing to do with contracts. It is about a promise with people at the club.
Relax"I was disappointed because I had signed a three-year contract and the plan was on target - despite two or three poor results.
"Believe it or not, the results at the end had nothing to do with it.
"You have to be relaxed and you have to trust in the people you are working with.
"I am not going to go into it but I must have said it about 5,000 times when I met Niall and the owners of the club that I would do it my way, particularly in team affairs.
"You might be better asking Niall or Ellis Short the reasons why I left the football club.
"But the time had come for me to leave, without a shadow of a doubt."