Not only Chelsea, but Tottenham is also studying how Chelsea defeated PSG, even though in the end, they had to lose. We can see how poor Tottenham's performance was last season in the Premier League. They were at the bottom after the relegation zone. Facing PSG because they won the Europa League against United. But they almost won against PSG.
Every match will certainly have a different situation. PSG is clearly favored, and they indeed have the advantage. But Tottenham also did well. Whether Tottenham is better or PSG is declining.
To be fair this Tottenham looks better than last years Tottenham, the managerial change definitely helped them out. I am guessing that they were a better team when they were facing PSG. Still PSG should have won easily, it was weird that they almost lost. They won in the last 5-10 minutes basically, otherwise they would have been the loser sand PSG losing two back to back finals would have been horrible for them.
The real question is, did PSG play badly and that's why the game looked like that? Or did Spurs played great and the game looked like that? I believe there was a bit of both. PSG wasn't "that" bad compared to past, and Tottenham was a bit better, so when you combine those two together, you get a good result.