Galtier should have given the trio of Neymar, Mbappe and Messi a chance to play together against relatively weaker teams. In the World Cup, they played with completely different squads and different match tactics. Both PSG's squad and match strategies are different.
The trio don't have problems to connect with each other and play well together. Their problems which actually exist are they have conflicts of interests and powerful ambition so that they don't want to combine together and fight for a general aim of the club. Especially Mbappe who wants to hunt for his personal interest than for PSG interest.
I don't think my words are so harsh for Mbappe. Previous seasons, he made many assists to his team-mates but in the past two seasons, especially this one he mostly does not want to make key passes and consequently so limited assists to his team mates. It is not coincidence and only can be explained by his selfish mind and too high ego.
Messi and Neymar are different and they are so readily to contribute to a general aim and operation of PSG. They made key passes and assists to Mbappe but did not receive the same contributions backwards from Mbappe.
However, PSG will now need to return to form very quickly. Out of 3 matches, they have lost two crucial matches. And if they lose one more match, the top spot in the table will be in doubt for them. If Galtier fails to make the right decisions now, and can't stabilize the match strategy, it will be difficult for PSG to win the Ligue 1 title.
PSG are no longer at a comfortable position in Ligue 1 but if they want to win it and play seriously, they will take the trophy. I don't worry that PSG want to win it seriously but fail to take it. They can definitely.