Just a few seconds before Chiesa scored, the camera caught Milik and Danilo standing by the line, ready to come in. The minute was 81 and Nonge had been subbed in during the 76th minute. It's impossible for Danilo to have been set to replace Nonge at that point.
Then we scored and Allegri decided not to make the changes.
It was only after the penalty and the slow reaction of some our players to the rebound (including Nonge), that Max decided to make the substitution.
I don't see a tactical reason for the Danilo for Nonge sub. None at all. Imo it was a hasty decision made in the heat of the moment. Allegri was furious with Nonge and he replaced him. He would have replaced him with a goalkeeper if necessary, just to punish him.