The volatile Italian was sacked on Sunday evening just five games into the Premier League season and less than six months after taking the reins.
The Black Cats have only managed three wins in the 13 games played under Di Canio with none of them coming in this campaign.
Quinn believes the decision was brave and has suggested the decision to accuse his players of having "rubbish in their brains" after a 3-0 defeat at West Brom may have proved decisive.
"It's a quick decision - some will say too quick," Quinn, who briefly managed the Black Cats, told Sky Sports News.
"They're making a quick decision on this again and looking back, the support Paolo Di Canio got in the summer with the players he brought in, I honestly thought he was going to get longer, no matter the start.
"If we start to peel the layers off in the coming days and find out what life was like under him from various players, you'll probably see a story that says this was a guy who did things in a totally unique way and by the looks of things, the players weren't buying into it.
"They've made a very brave decision to appoint him, they got what they wanted out of him, and now they've made a brave decision (for him) to go.”
Quinn, however, believes he would have probably have tried to give people as much time as possible.
"Something tells me there's a little more to it as well," said Quinn.
"It was perhaps they felt that the players were finding it hard to conform to his unique style. I think that might have played a part in it as well.
"They've made such a brave decision now.”
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