Nearly all German clubs do it. Tuchel, Klopp both were nobodies on the big stage prior to Dortmund. Nagelsmann was nonexistent prior to Leipzig. So, the german clubs except for Bayern don't really hire big names, but look to bring in talented guys who can become great. Even Bayern are known to make bets with new-wave managers (see Kovac, Flick).
Dortmund now hired Marco Rose. Could be the next interesting German manager to have soon make his debut on the big stage.
Klopp brought Mainz into the Bundesliga for the first time in its history. Tuchel managed Augsburg and played magnificent football with them. When he was appointed as Mainz's coach, he inherited a 2nd division squad and managed to produce good results relative to the talent of his squad. Then he was appointed as Dortmund's coach.
Nagelsmann wasn't nonexistent prior to Leipzig, you were just unaware of him. He was already considered one of the best young coaches in Germany when he was managing Hoffenheim. I know this because he was the "hipster pick" for manager choices on reddit/twitter/instagram back in 2017. lol
He was appointed as Leipzig's coach because with Hoffenheim, like Tuchel, he massively overperformed relative to the squad's talent. Revolutionized the team's football, had players like Joelinton massively overperform, and more. He was already linked with Bayern back when he was managing them. In fact it was pretty huge news when he revealed his rejection of Bayern (which prompted Bayern to go for Kovac ).
Kovac also had relative success with Bundesliga clubs prior to Bayern.
Flick was the architect to developing the DFBs football back in the early 2010s, and was championed as being one of the main reasons they won the world cup. He was also involved with Bayern's hierarchy for quite awhile before being appointed, especially in roles such as assistant manager.
All the examples you brought up either had massive relative success with lower tiered clubs in Germany's 1st and 2nd divisions. The one exception being Flick, who was responsible (alongside Low, the players ofc) for Germany's success in international football. Not to mention these examples all spent an insane amount of time climbing the football pyramid through less admirable positions (assistant coaches in 2nd/3rd or even amateur teams) because they weren't professional footballers or were but weren't good enough to be handed coaching positions on silver platter like Xavi is. These examples are all a stark contrast to the argument you're trying to paint: that top clubs in germany hire coaches with little to no experience.
No, hiring Xavi is not analogous to Bayern or Leipzig hiring Nagelsmann or Dortmund hiring Tuchel and Klopp. Try the FUCK again.