The former Celtic and Aston Villa manager left the Stadium of Light at the end of March after just 15 months in the post.
He was replaced as boss by Paolo Di Canio and Short, writing in his programme notes ahead of Saturday's game against Everton, said: "The simple answer as to why we changed managers was because our results and performances on the pitch hadn't been good for over a year.
"The decision to change manager was made with only one aim: To give us the best possibility of staying in the Premier League.
"I am excited that we were able to bring in Paolo. Paolo is a real training ground coach.
"His very choice of title of head coach, rather than manager, tells you a lot about him and his approach.
"He's a real student of the game, spending hours on the training ground every day.
"He had great success at Swindon Town in taking a team that he was given and training, organising and motivating them to win.
"In my initial discussion with Paolo, I was very impressed with his enthusiasm, his passion and his love of the game.
"I like his willingness to do whatever he and his team have to in order to give us a successful end to the season.
"Additionally, his confidence is also an asset and in the brief time he has been here, the feedback from all areas of the club has only confirmed those qualities."