Mbappe is one of the best football stars in the world and one of PSG's most important players, so PSG have high expectations from him. PSG have managed to keep a very talented player so far, no matter how talented Mbappe is we tend to forget that he is one and he will never play like 10. No matter how well a player performs in a team, if the rest of the team's players do not provide good support, then the team's performance will be null. Mbappe is performing well individually for PSG but all the other players in the team are not able to support Mbappe well due to which PSG is not getting good performance as a team. Mbappé has been heavily buzzed about outside the club in the transfer window ahead and chances are the buzz will come true.
This is exactly what I've been saying all along a situation where by there's a good player who helps the team with some good performance which should get the team to a good position very fast but the rest of the team members are not optimal, it will end up jeopardizing the efforts of the star player.
A typical example is when the players scores several goals for the team in a match and the defenders alongside the keeper is unable to guard their post well enough not to conceding too many goals that will bring the goals scored by their player to a ruin. In the case of PSG mbappe alone can not do all the team needs to win UCL but with the help of other team members and good cooperation they can achieve it because they have got a good dept and on the other hand I think the coach is also a problem to the team too. The major challenge PSG has always gotten has been with the UCL as they literally win the ligue 1 at will.