Earlier quoted context omitted.
Keep in mind that the employees in Amazon warehouses are there of their own free will. So, however badly they are treated, Amazon is apparently providing an option to them that's better than any alternative they may have. Surely, that's better than them not having the option to work at Amazon at all.
In what hypothetical world does Amazon disappear and no other business takes its place?
In the current world workers choose to work there.
There are usually many other choices available that were discarded by those workers. What if all replacements were just like those numerous other companies that the current workers didn't choose? That seems more likely than some company appearing that gives them vastly better options.