Real Madrid won La Liga and Champions League last season without Mbappe and this player only came to their club this summer, and had several matches for them. It's important to remind a fact that Mbappe struggled in early matches for Real Madrid too. He is a super star player and will be more important with Real Madrid with time, but at this moment, in his early adoption there, he is not too much important with them. Attributing a loss because of Mbappe, is not closely to actual reason.
Euro 2024 and Coppa America 2024 in this summer actually affected many star players who returned to their clubs with injuries or exhausted bodies and were not too ready for a new season.
Yes, it is a fact that these competitions exhaust the players and leave them with very little room to rest, however now Madrid cannot afford to lower the level, both in the League and in the UCL, it must also be noted that Ancelotti's work has been very good, to manage these players and always make accurate strategies is not easy, however I have realized that Ancelotti uses Mbappé as when he used Benzema, he has him like a secret weapon that he launches at the last minute to win games, it may be because he takes care of him or because he sees that he lacks some things to compact the team, however somewhere I saw that Mbappé sent his national team a warning that the French games that are played officially are really necessary, perhaps to avoid injuries that affect their clubs.