Maybe Real Madrid will not care much about the upcoming El Classico because they have a match against Bayern Munich and they already have good position and points on the table, so why to rush and risk against Barcelona? Barcelona has nothing to lose while Real Madrid might be in trouble if Barca plays tough and RM's players get injured. They want to preserve their players for the match against Bayern, Champion's League is very important for them and their points in La League give them a good advantage and excuse to even lose 1 match or end up with draw.
Real Madrid have now reached the semi-finals of the Champions League and of course Bayern Munich will be a difficult opponent for them later, but when you say Madrid no longer care about the game against Barcelona, obviously you are very wrong man, because againts barcelona very important for Ancelotti to be able to grab the two remaining trophies for Madrid this season. Throughout the season Madrid have been fighting to reach the top of La Liga, then when they are only one step away from winning the La Liga trophy why do you think they will let it go this season?
In my opinion this match is clearly very important, even if it's not to confirm the La Liga trophy, but fighting Barcelona is about pride. The two of them have become eternal rivals so playing without any reason for a trophy will definitely show each other's best performance, especially since this is still in a competition where 3 points means a lot to both of them. Barcelona needs to be further away in points from Girona and Madrid too, having more points automatically means Madrid has more time to prepare for the UCL competition where the opponents are strong teams. Bayern Munich in Tuchel hands reminded him of when he was still at Chelsea and facing Madrid in the UCL. Tuchel seems to have been given another opportunity to take revenge but with a different team and squad.