In this season Real Madrid was a little bit unlucky because they lost their forward Karim Benzema and they couldn't hire any other player to fill his place and then their defender got injured hardly in the first weeks, also Thibaut Courtois got injured and Real Madrid knows he can't play for weeks, after that they hire another goalkeeper to fill his place in the next games.
When Kepa Arrizabalaga joined Real Madrid and they spent too much money on him, the fans of Real Madrid were worried about his performance but Arrizabalaga had a good performance in the previous trainings, also he attracted Anceloti's attention.

Indeed, all this was bad news for the Real Madrid squad when the La Liga competition was about to start and after that there were still players who were injured. His absence was unmitigated, even among them there were those who until the end of the season would not be able to strengthen Real Madrid. Kepa's arrival at Real Madrid is only on loan and of course it won't cost a lot of money. Ancelotti does like Kepa and even threatened Lunin's position, which was previously expected to get a starter when Courtois was injured. I think Ancelotti must be fair in dividing the rotation for these two goalkeepers.
What do you deem to be fair? If one goalkeeper turns out to be playing better than the other, do you think fairness in professional football means to let them both play? I can think of a rotation solution for some time, but if one really outplays the other, I guess sticking to one goalkeeper is the better choice. I have never really liked rotating goalkeepers especially when they have different styles. When one goalkeeper is very good on the field as well and likes to accelerate the game with high precision passing and the other goalkeeper is rather known for slowing it down, it always means a change in defensive strategy for the whole team every single game there is a rotation. But we will see how this develops in the coming weeks.