Bonucci didn't leave because of lack of playing time, and losing his spot in starting XI to a superior player. He left because he was an arrogant douche, who thought to highly of himself. He learned his lesson and has been eating humble pie ever since.
Benatia left because he's a wimp who's afraid of competing for playing time. Probably why Allegri didn't play him much this year, and prefers Rugani instead. Realized the Moroccan Malaise had his sights set on Arab retirement league. Didn't want that pathetic attitude here any longer.