Majority of people underestimated PSG in the beginning of the competition. PSG struggled to their last match in the group stage and they have to win that match to enable them qualify for the play off. They became bold and confident in themselves.
Nobody saw them to be the favorite even till the finals. It was when the match started that we saw a different thing entirely to the opposite of our predictions. Barcelona super form ended in the semifinals with a strong fight against Inter but got defeated.
Yes, I did too. Nobody rated PSG high enough until the eliminated Liverpool in the round of 16. Nobody expected that because Liverpool had the best results out of all participating teams in the league phase. I think winning that game showed them that they can beat any team if they decide to do it. That's why it's always wise to stay focused on the task at hand even if you didn't have the best starts. The fastest horse doesn't always win in the end.
Also, I love a good underdog story such as PSG winning their first UCL and Atalanta stunning Liverpool in the Europa league a few years ago before going on to hand Leverkusen their first loss in their unbeaten season in the UEL final last year.