(Note: This is simply my recollection. May not be completely accurate.)

MC and Group see the killing. The group loses faith in the upper command. Places said faith on Xu Jun. As in pledging an oath of loyalty directly to him. Xu Jun realizes that this would be treason. However, it's not like he can refuse and report his subordinates for treason right? So he accepts the oath. (Big deal cuz the Army is only supposed to be loyal to the Fuhrer.)

Hitler receives word of this. Is infuriated.

Apparently, Jack, when in Reinhardt's body, had set up a behind-the-scenes organization. (I think) And can be said to be the true leader of the Party. Then, Xu Jun (With Reinhardt's influence) is able to coerce the resignation of the senior Wehrmacht and Army commanders.