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.
I personally bet on Chelsea to win, everyone told me I was crazy but in the end I managed to prove them wrong, it wasn't easy, my heart told me I had to bet everything on Paris Saint-Germain, but in the end I made the right choice,and the choice paid off