Bayern Munich seems reluctant to let Joshua Kimmich go but unfortunately, it is not in line with what the player concerned wants because as far as I know, Joshua Kimmich is not interested in extending his contract, which means he could leave this January or at the end of the season as a free agent. Besides Real Madrid, Liverpool is also reportedly interested in Joshua Kimmich. It seems like Liverpool wants to anticipate if Trent Alexander Arnold really leaves Anfield.
If his contract is not extended then the player's status will be a free transfer so it will not benefit Bayern Munich. When a player does not want to extend his contract for certain reasons and the duration of his contract ends then the club will definitely consider releasing him. Real Madrid can take advantage of this condition because they often make efforts to buy players with complicated conditions but in the end they win. Trent Alexander Arnold's uncertain future conditions make Liverpool interested in him as an anti space step and maybe they can make an appropriate offer to Bayern Munich.
What I see from Kimmich is that he now has the most ideal option to join Madrid. No matter his free transfer status, but Kimmich has a better future. That's why he is reluctant to extend his contract. In Madrid he can have a bright future and a decent place as a player as long as he can show his quality. At least in Madrid he can be closer to trophies especially the Champions League.