Benzema was the only reason Real Madrid didn't win the title last season. Real Madrid were overly reliant on Benzema. But Benzema's performances have been somewhat erratic due to several injuries. This is why Madrid had trouble maintaining consistency in performance. Next season they are trying to add a suitable replacement for Benzema to the squad. Perhaps we are going to see Mbappe as Benzema's replacement. If Mbappe joins the Madrid squad, Madrid's attacking performance will be stronger.
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.