Unions are fundamentally democratic organizations, and without an obligation to represent, you can easily find yourself in a position where your politics within the organization matter more than your circumstances.
All of this stuff is mostly a distraction. AT&T wireless is a union shop, and is very competitive in the marketplace. When you have companies that are fat and poorly managed, with the ability to dump costs on the customer, like Boeing or GM in the old days and you get shitty, poorly negotiated contracts,
In a case like this, AT&T has unlimited leverage. Much of their area are in labor-unfriendly states, and they have a pliant FCC who would take action if AT&T decided to start killing kittens. So they’re acting while the Fox is still in the hen house.
(They still do, sometimes, and then they take the flak in the eyes of the public, deservedly).