a little surprised by the transfers that Real Madrid is currently making, they now have a lot of midfielders, and if you look at the midfielders they all have the same quality so of course there will be fierce competition to be able to get the main place.
Arda Guler is an investment for the future, he is only 18 years old and Real Madrid does this a lot, as was done with Martin Odeegar and now Arda Guler is back like that again, the chances of him succeeding at Real Madrid are slim in my opinion, but this is enough to be a stepping stone in order to develop.
Firstly, the club is in the active phase of restructuring (Modric and Kroos will leave next year) so it is obvious that Real Madrid needs to try different options plus prepare replacements for the main players in advance. Secondly, as always, Real Madrid will have a super busy schedule of games due to the fact that they are aimed at winning all competitions, so they need reserves for rotation.