Di Canio was relieved of his duties after Saturday's 3-0 defeat to West Brom left the Black Cats with just one point in the Premier League, and without a win this season.
While Quinn says he would have given the Italian more time, he suspects dressing room unrest played a key role in his swift departure.
"It's a quick decision - some will say too quick," the Irishman 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."
Quinn says that both the decision to bring the Italian in and the one to let him go were brave from the club, and thinks that the players were struggling to adapt to his style of play.
"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," he said. "It wouldn't have been my style. I think I would probably have tried to give people as much time as possible.
"Something tells me there's a little more to it as well. 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. Will it pay off for them?"