Dest was too cute with Mbappe in the first leg. Mingueza and Firpo had the correct approach: just be on his heels all the time, shove, be aggressive and foul when needed (Mingueza was overeager in this regard). Dest in general lacks this aggressiveness in defense for now. He plays as if he hit a huge blunt just before the game
Dest also just came back from an injury before the first leg and probably wasn't ready to start (won't even talk about Pique) but you're right.
I think it was Rafa Marquez who once said something like "I'll go hard on the striker I cover in the first 5-10 minutes, maybe get a YC but then I won't have to worry about him much for the rest of the game."