I still don't understand one thing. Why did Nagelsmann wanted to manage a national team already now? I mean he is a really young manager after all. He was climbing the steps really quick in his career as the last club he managed was Bayern Munich as you know.

After that I really expected him to continue managing big clubs like that.
I think national team jobs are a better fit for managers with big careers at a little old age minimum too. Because you are like a little active than being retired while managing a national team.

You are rarely playing games.
In his last spell at Bayern Munich he had some failures. The possibility of the same thing happening again could have created even bigger problems for his career. I think the German national team are a comfort zone for him. He will continue to get good stats with the German national team. But if he had a second big team experience after Bayern Munich and failed, there would be a lot of negativity about him. I think the German national team are a comfort zone for him and an opportunity to rest. He can have an active rest there for a while.
Failure has become a risk in coaching a big club. There is no coach who has pursued a career without problems. It takes a long process to achieve success. He is still young and needs a lot of experience to become a great coach. If he just stays in his comfort zone, he won't get a lot of good experience. he needs to think about his future, not just stay in one place, I know he has good potential, it's just that his dismissal at Bayern Munich made him step down from coaching in the big leagues.
If he doesn't want to coach a big club which is full of pressure, he can coach a mid-table club in the Bundesliga and improve his performance, who knows, maybe that could increase his value. Slowly start to train mentally and be confident again to be able to coach a big club.