They shut down because they lost customers after the union threatened to strike. The hit to their stock price, even after the union withdrew the threat, meant t

They shut down because they lost customers after the union threatened to strike. The hit to their stock price, even after the union withdrew the threat, meant they couldn't get more funds to continue operations. Perhaps they could have raised prices earlier and gone out of business faster, but it's pretty clear that the writing was on the wall for Yellow for quite awhile.