I have done some analysis before the final and came to know that PSG has conceded only one goal in 6 matches of the tournament before the final and that shows they don't have good attack but also good defence.
From the analysis that most people did before the match, most people were just so sure that PSG will be winning the final, their performance was so good from the group stage till the final, they conceded just a goal, they played against some top teams, and PSG humiliated them in the match, and they were able to win the champions league, PSG performance have just been so good, and everyone already underestimated Chelsea, they believed Chelsea got to the final by luck, because they didn’t play strong teams like PSG did, and they believed their is no way Chelsea will win PSG, but everything changed at the end of the match.