Paris Saint-Germain will come out ontop because they've been the best leading club in the world when it comes to performance. They've been extremely counting good scores and winning games, always been on streak winnings. Everyone is underestimating the rating of Chelsea when it comes to the club world cup. It's been an erratic time to be a Chelsea fan because they're still building their team from scratch and there comes with formidable changes. Enzo Maresca have been an important member for Chelsea, with his presence, they've been able to be on streak winnings and accumulating trophies.
There is no doubt that Paris Saint-Germain has a better chance of winning this match, but overconfidence can be dangerous and Chelsea should definitely not be underestimated. Because they didn't come here automatically as you already mention that they starting from the scratch and as well the maintained performance took them to this final match. Maybe the Chelsea team we see now will be even stronger in a few years.
And besides, I wouldn't be surprised if Chelsea were able to beat Paris Saint-Germain tomorrow, I've already explained the reasons. But the expected result is PSG will win.