The thing is, they aren't their rivals. Not really.
Schalke are bayerns arch-rivals, and Dortmund are their real modern day rivals.
Wolfsburg have only won 2 trophies in their 71 year history, the 2009 Bundesliga, which they won because Bayern were in a complete shambles on and off the pitch, and the DFB Pokal last year - which they won because they lucked into KDB.
With KDB they finished 2nd last year - mostly because Dortmund, Schalke and Leverkusen had abnormally bad years. This year, they'll struggle to say 2nd with De Bruyne, and without him, 5th would be good.
So that is why they are subserviant. It's a midtable club which lucked into a high finish last year, not really expecting to ever compete with bayern.
Not to mention they share fucking board members!