It is not easy for psg in the Champions league. The champions league is the toughest league you can think of. PSG is leading the French league because their are no strong teams that can challenge PSG.
The champions has many strong teams competing to get the championship.
in the champions league, PSG is the favorite team to win, but seeing the quality of their performance in the last few matches, I doubt they will be able to win the champions league, the thing that really doesn't make sense to me is because they were beaten by Rennes twice this year just. that means rennes is a stronger team than PSG, totally unexpected.