Despite the more recent disparagement of organized labor, its power did not come about by happenstance. At its highest level of importance, unions brought attention to the workplace horrors of their time and were responsible for many of the protections now in place for every American worker.
As happens often, however, that power led to corruption and excess. The loss of union influence was much of its own doing as labor organizations failed to adjust their demands to the realities of industrial evolution. When it became easy for companies to shift production overseas for a pittance of what American workers were making, they did so.