From the sounds of it, its mostly the bad loans + poor management part that killed Yellow. Management of the company have been asleep at the wheel for some time now, union demands are not likely the precipitating factor here.
EDIT: All I'm pointing out here is that I don't think this can land squarely on union demands, which is what I think some of the press are making it out to be. The actual financial mismanagement of the company precedes anything the union was asking for (which in part, was for Yellow to live up to their previously agreed obligations)
It doesn't seem like the "union demands" killed the company narrative tracks here, since the union demands were things like "You should actually make the contributions to our retirement accounts that you're obligated to make."
The threat of a strike was the final blow, causing them to lose customers and dropped their stock price such that they didn't have anything to borrow with.
All of the bad decisions they'd previously made out them in this position, but the union threatening to strike was the straw that broke their back- despite the union withdrawing the threat.
That last tidbit probably tells you all you need to know about how little chance the company had at surviving.
The company entered into questionable acquisitions though largely to try to become more competitive in the LTL market with their non-unionized competitors. Now they executed the mergers poorly and failed to integrate for too long, but even some of those integration challenges were due to union considerations. So yes management was incompetent but I think being unionized did play a large role in their demise as well.
EDIT: All I'm pointing out here is that I don't think this can land squarely on union demands, which is what I think some of the press are making it out to be. The actual financial mismanagement of the company precedes anything the union was asking for (which in part, was for Yellow to live up to their previously agreed obligations)