Never had a Manchester United fan ever supported Chelsea to winning any team they are playing against in any competition even if that team is one of the worst team from Bengali. So it's not surprising to see a lot of Manchester United fans not having hope in Chelsea having any chance against PSG in the CWC finals. What I just wait forward for is 13th July, when the ball bounces we can all seat with a bottle of beer in hand and watch from our respective locations. 
Fans might support any team if the win will be favourable to their club. An example is if Chelsea winning Manchester City will make Manchester United win a trophy, the Red Devil fans will support the Blues. But I will have to confess that United fans have a deep hatred for Chelsea. But we shouldn't be surprised that the English side will put up an outstanding performance that will silence critics. Please, I would love to join you to watch the match but I would prefer a bottle of wine.