After experiences with Neymar or Lionel Messi, the French club is determined to turn the project around, with or without Mbappe. They will have to accept that the project with Mbappe, Neymar, and Messi has failed. Could not help PSG achieve the most desired trophy, the Champions League, even though at times PSG had all the stars. And if you think positively, parting ways with Kylian Mbappe will help Paris Saint Germain save more than 200 million euros to pay this player's salary. That amount will be invested by PSG in transfer activities. PSG is a financially rich team, I don't believe they won't be able to find a replacement for Mbappe. Besides, coach Luis Enrique also has other quality players like Gonzalo Ramos or Kolo Muani, ready to replace the position left by Mbappe.
The experience with Neymar and Messi should have made PSG understand that they should not just invest in big players only to be able to win the champions league but then they still went ahead and had almost most of their investment thrown around in mbappe meanwhile they would have used the opportunity to see how well to build the team such that at this point of his exit, they wouldn't be struggling to get replacement for him or getting to still maintain their good form even in his absence. Now they can understand better and start to build a long term strategy to help them to win the champions league one day in the future. PSG has all it takes for them to start to make preparations for the future for a chance to win the champions league which I believe it's very possible if they are able to maintain a consistent strategy to growing and improving their strength beyond the level of the their domestic league to look fit beyond the regular teams who compete in the champions league and a re used by the bigger teams to get up the champions league table and having a chance to win the champions league trophy.