The season start was clouded by concerns about the code's integrity, given both the ongoing anti-doping investigation into the Bombers and the league's recent sanctioning of Melbourne for the questionable way they went about securing a priority draft pick in 2009.
Demetriou admits the AFL had to act to restore supporters' trust.
But he believes the league's response, which included expanding its integrity department, increasing penalties for breaches and auditing all clubs, is paying off.
"To restore the trust in the game these are things that we have to do," Demetriou said at a Greater Western Sydney lunch in Sydney on Thursday.
"Most recently this faith has been tested.
"But it is clearly alive and well as evidenced by the way our supporters have turned out in record numbers over the first three rounds of the AFL season.
"It's the first time ever in our history over one million people have been to the first three rounds.
"They've voted with their feet."
He said last year's record club membership figure of 707,621 had also been exceeded.
Demetriou praised the way the Bombers were cooperating with investigators.
And he distanced himself from suggestions Essendon coach James Hird should stand down.
Demetriou was angered that his comment last week that Hird had to consider stepping aside, was wrongly portrayed in some quarters as him urging the Bombers coach to quit.
"I never suggested that. What I said was that would form part of his thought process," he said.
"He's got every right to put his best case forward."
Demetriou - who last week described allegations about supplements given to Bombers players as shocking and disturbing - said Hird was entitled to a presumption of innocence.
"It's something that we should all hold very sacred in this country," he said.
