Dein was the co-owner and vice-chairman of the club until 2007, and since then Arsenal have failed to win the league and have not triumphed in any competition apart from the FA Cup.
Speaking to TalkSport, Wright said: “With David Dein going, that was the beginning of the end.
“He's the kind of person, in respects of football and knowledge and vision and love for the club, who you can't afford to lose."
"Decisions were being made, in respect of Aaron Ramsey's contract, before it was starting to run down and were being made by people who were no longer there," he said.
“So we are talking about a £60million player that should have been a case of 'OK, we will have to sell you now' and not let it get to a stage where it has got to."