The club president decided to let the players go? Laughs... Neymar went to Saudi Arabia on his own for money, Messi left the club because he was uncomfortable being there and we all remember how he was treated, and Mbappe waited until his contract expired and left on his own. Remember, Mbappe didn't want to play at all when they realised he wouldn't sign a new contract. So it wasn't the club president who decided to do the bold move
I don't see patterns between these players. Neymar was useless for a long time for PSG, like he did with Al-Hilal, so he joined PSG for the money with his famous escape from Barcelona then he indeed left PSG for the money but also because he wasn't helpful for the team at all.
Lionel Messi joined PSG because he has friends there and to stay in Europe, otherwise he didn't find peace nor the help from his teammates so he decided to leave.
Kylian Mbappe is another story. He was in PSG because he is French and playing in the best team there to join later his dream team Real Madrid. In fact the French president and PSG president, made a lot of pressure on the player and his family to force him to stay, which was a mistake by the way.