Well they did exactly that with Hakimi who was probably one of the best right-backs in Europe last season and will probably be a brilliant player for Inter.
Madrid can do that and just not care. They're fully packed in midfield and play a 4-3-3 under Zidane – he is more of a 10 IIRC.
They have Hazard, Rodrygo, Vinicius, Asensio, Vazquez for the wide positions, and Isco, Kroos, Valverde (who is superb, Modric, James, Casemiro etc for the middle.
They probably have seen the success of Hakimi and reckon they can do the same here. As another poster has said, he either develops into a brilliant player for Madrid, or they can sell him on - whether he's played brilliantly like Hakimi has or if he's struggled. But given it's the Bundesliga, in one of the best teams, then it's the right place for him to be.