Madrid always shows that they are more interested in the Champions League than the La Liga because Madrid can choose to channel all their energy to the Champions League rather than the La Liga, so when it comes to the two, we already know which one they are choosing and they are so experienced when it comes to the champions League, and when you are playing against them, this is something that you just have to be careful when you are playing aginst them, and this is why when it comes to the Champions League they call them kings and atheltico is also trying there best to earn their title, and it is now going to be between all of them, that is real madrid, barcelona and atheltico madrid it is going to be between them for sure. You can not compare Athesletico Madrid to Real Madrid, especially in the Champions League.
It's not like they use to show, they have this way of being stamina in anytime they play in Champions League and Anceloti knows how to coordinate his bird to play very well. He doesn't even joke with the players he chose to start or end the game, everything must be organized that's why he doesn't even allow unexperienced players to have a taste of those games, this is why they do have that chance of winning in every Champions League game they play.
Sometimes, the available teams makes a difference in a every competition. You will see that Real Madrid do well in Champions League and fumble in domestic league, it's not like there is magic or something like that, the teams in domestic leagues don't have anywhere to go and as such, it becomes their main focus than, they don't jock about it but teams in multiple leagues are mixed with the ones that are serious with 2 or 3 leagues and the ones with many more leagues.