I don't think Mbappe was an obstacle to PSG's success. mbappe is undoubtedly a great player. He scored a lot while at PSG.
After Mbappe left PSG, Luis enrique got the opportunity to work well with the squad. Earlier, the team only depended on Mbappe's performance. But now the team is not dependent on any specific player . And this is one of the reasons for PSG's success. Every player in the squad is giving full effort in their position to perform well. Luis enrique will undoubtedly fight for the Champions League title next season as well. And PSG's overall performance seems to be very consistent so far.
Mbappe wasn’t an obstacle to PSG, he even helped the team to get the fame they have now, he scored a lot of goals for the team and won a lot of trophies; but then, they don’t have good coaches to work on their teamwork that is why the players depend on Mbappe to be scoring goals for them, they didn’t work of the team’s teamwork to help other players in the squad, they allow Mbappe to take all the game and left other players behind.
Since Mbappe left PSG, Luiz Enrique came in and improve the team in good good form, he make sure they have teamwork and relay in no single player which has helped them to win the Champions League and now making effort to win the FIGA Club World Cup.
Now, PSG will face Real Madrid, it will be a battle between Mbappe and his former team, and Mbappe is yet to win a single trophy since he joined Real Madrid; therefore, all eyes will be on him because fans will be expecting much from him and he will like to score goal in the match to proves to the world that he made the right decision joining Real Madrid.