Not only you but I am also surprised by PSG's performance and I myself did not think at the beginning of the Champions League season that PSG could play in the Champions League final. There is enough reason not to think so, when Luis Enrique took charge of PSG, he sold several players from one club to another, and one of the team's players, Mbappe, left PSG, so naturally I thought that maybe PSG was going to end a bad season because they did not have a big striker in their team, but still, due to Luis Enrique's skills and experience in managing the team well, PSG was able to qualify for the Champions League final. I wonder what Luis Enrique would have done now if this team had secured the Champions League final with this team, if PSG had the same team before.
PSG began this season in Champions League considerably worse than their starts in past seasons and surely I was similar to you, and did not think that PSG will went to far like this. From their bad start, they have been actually improving a lot so that they are capable enough for beating many strong opponents in later rounds of Champions League. Their appearance in the final match is not a free gift from any club, they worked so hard for it and they are well deserved with a slot in final match.
Looking at PSG performances recent months, they truly had better balance than past seasons with many attacking players at world class, super star players who don't mind to contribute for a whole team defense proactively. Now they fixed that big issue successfully and are ready to beat a last opponent, Inter Milan, for lifting a first ever Champions League trophy in their club history.