Yes, actually, Rennes is not that strong, however, PSG had quite a hard time beating the club with more goals. So that the only goal from Mbappe was PSG's winning goal in the semi-finals of the France Cup. Mbappe, once again, was the decisive winner at PSG.
Meanwhile, PSG will play against Lyon in the final match of this France Cup.
PSG should also be able to win, because if you look at the strength and solidity of their clubs, PSG is far above them. So that makes PSG superior in various ways. In this case, if PSG loses, this will be very embarrassing. But I don't think they will lose against Lyon, they shouldn't.
PSG played pretty confidently in this match and the player that is going to leave the club at the end of the season, the best player of PSG, mbappe, has scored the only goal of the match. I am starting to think about what will happen to PSG after he leaves.
Anyway, this was the semi-final of the French Cup. And by winning this match PSG is going to play in the final of the French Cup. They will play the match against Lyon. Remember Lyon has not performed very well in this season. Even though they are improving right now, they are still at the middle of the table. So I think it is not going to be a problem for PSG to win the final as well