Unions prioritize whatever it is the members want prioritized.
A recent example: the WGA just ended a strike against the movie and television studios and from what I've read about it, the resolution was not determined by the loudest minority. A deal was worked out, the membership voted, and 99% voted to accept the agreement. That seems like a success.
I have a feeling a large % of them will not be in WGA jobs in 18 mos