We can't blame someone when they fail to win a title after all in the team there are 11 players all players have the same responsibility
The more appropriate reason is that this season Barcelona is better prepared and playing better so that Barcelona is more deserving of the title
In the following season the two teams did not change much but there is no guarantee Barcelona will win again could be Madrid taking over.
In some cases, we can blame someone. For example, Mbappe promised a lot of things to Real, but then extended the contract with PSG - as a result, Real was left without Mbappe and without Haaland. I don't think anyone else's fault can be found here other than Mbappe. Although then, of course, he acted in his own interests and thought that he was doing the right thing (how wrong he was hehe).