Yes, this is politics-related, give me a second.

Rumors say that the team is divided: On one hand, you have the "Bavarians" (Who played for Bayern München, the most successful German team, so they have lots of players in the national team), who are mostly white, like Müller, Hummels and Neuer.
On the other hand, you have the "Foreign Legionnaires" (These titles are from the German media, seriously), players who mostly come from foreign clubs and/or have non-German ancestry, like Özil, Khedira and Boateng.

Basically, these two groups dislike each other based on politics (The Bavarians dislike the Legionnaires because of the Erdogan scandal, (where players Özil and Gündogan basically said explicitely that they consider themselves Turks and not Germans). OTOH, the Legionnaires are insulted that the powerful Bavarian "lobby" didn't intervene when the federal coach Joachim Löw (Yes, Jew, whatever) culled Leory Sané (Another nigger) from the national team regarding the world championship.
Supposedly, members of these competing groups don't even sit together during breakfast.
As expected, such things lead to people not playing together on the field.

This whole fiasco shows the fragmentation of Germany as a whole, a microcosm that accurately depicts the macrocosm of the country. It's an unheard-of escalation of the political conflicts of this time.