On the surface, one might think that a black eye on the UAW for getting beat in Tennessee was the big story. It's not. The big story is what happens next:
So if VW moves forward, and sets up the Works Councils, the UAW has a choice to make: Do nothing, and appear weak to your members (and other organizations that have UAW members working there), or sue, and quite possibly lose.
Neither one is a good outcome for the UAW.