Which players do you mean? From what I know, there is 1 injured player now (Ferland Mendy).
So, it is untrue that many players of Real Madrid are injured. Check again their squad information:
https://www.transfermarkt.com/real-madrid/kader/verein/418They played very well in the current El Classico. So, they have no problem with their performance.
For the previous matches in La Liga, they didn't play well constantly because Benzema often gets injured. But now Benzema is available, Real Madrid can have a chance to chase Barcelona again in 1st place.
you're right the only player who has been injured so far is mendy even that hasn't affected the real madrid squad at all this season because real madrid have some good substitutes in that position. mendy is also often the second choice for ancelotti this season.
However, at the start of the season, Benzema absence had made Real Madrid game situation unmanageable quite well, but that's not the right thing to blame them for. real madrid are still pretty strong this season but in laliga they have been a bit unlucky in a number of games which have cost them points.