Barcelona deserved to win 100%, they have quality, sharp strength even with 10 players still can't be penetrated by Real Madrid players. Bellingham and Vinicius under perform, Madrid most vulnerable defenders are in the position of Vasques and Tchouaméni who are indeed not suitable to be installed as defenders. Therefore Perez must recruit new defenders this season is his obligation if Madrid wants to have a solid defense. The score of 2-5 is still quite lacking considering how many opportunities Barcelona had to score a goal if Courtois did not save his goal. This is a heavy blow and an important note about Madrid very porous defense.
Not only Real's defense played badly, but also Real's strikers, because 1 goal out of two was scored from a free kick, and Mbappe scored the first goal at the very beginning of the match, when Barcelona did not expect it.
Mbappe as well as Vinicius almost do not work in defence line and in fact Real defends without them, at the same time Gavi, Olmo, Lewandowski retreat to their half of the field and participate in the defensive actions of Barcelona.
Except Bellingham in Real no one can create a real dangerous moment and Real probably counted on Mbappe's speed qualities, but this is not enough to beat such an opponent as Barcelona.