Ancelotti wasn’t lucky with the players Eder Militao missed a lot due to injury, Mbappe had to adapt, and Bellingham and Vinicius weren’t in the kind of form we know them for. I think Xabi already has well developed tactics and excellent training sessions that will generally prepare the players for the start.
Real Madrid headcoach, Carlo Ancelotti was lucky enough to have the best players around and these players was determined to win games and lift trophies, they got it in them to come out in every game with stellar performance. What change in the Real Madrid team? We've not any scenario where the best team will not come out winning consistently at the top. Eder Militao was eager to play but base on his unfit momentum, we watch him crumbled several time and became one lesser on the pitch. He couldn't meet up the desirable expectations and this got him some flopping performance and stats. He's not only the one but others included.
Real Madrid is definitely not the same team as it was a few years ago. Remember, Real won three consecutive Champions League titles when Zidane was the head coach. I believe Xabi can motivate them and elevate the team to a higher level. They just need to stay healthy and be in top form.