The reason is that Paris Saint Germain have not lose any match from the beginning till they got to the final, which was the believe people have that Chelsea will loose for Paris Saint Germain to win the title. People need to celebrate the victory Chelsea embraced from the final match because Chelsea they know over three seasons with poor performance, is the same Chelsea that defeated Paris Saint Germain in the FIFA club world cup, those that bet for the favour of Chelsea to win in that final match, won all their bets because Chelsea played the final match to scored three goals to cause heavy celebrations in the stadium, where different countries presidents celebrated Chelsea coach for the wonderful work.
After comparing both teams by looking at their statistics, it was clear that PSG was the favorite team. The stats showed that PSG was stronger than Chelsea, so almost everyone was expecting PSG to win the match even I was expecting it to be an easy win for them.So, when Chelsea won the match, it was a big surprise to almost everyone, as not much was expected from them. But one thing I tried to understand about the match was that Chelsea had prepared well for PSG and looked for the best tactics they could use against them. On the other hand, PSG was not well prepared for Chelsea. They seemed to think they could easily beat them, just like they had beaten every other team in the tournament.
This is one match which result has taken many by storm because it wasn't the result they had prepared for from their bets. And I won't really blame anyone for picking PSG, because their stats in the competition was 100% good compared to Chelsea. They won all the best teams in the tournament including Real Madrid, and this made gamblers to build so much confidence in them winning the underdogs Chelsea. But at the end PSG couldn't get 1 goal but conceded 3 before end of first half.