Globalization is certainly a very important factor but technology also has to be mentioned. In lots of industries it has massively reduced the bargaining power of the working people. Mostly because increasing output is much less dependent on labour than in the past.

Technology does not reduce labourers bargaining power. Legislating away workers protections, union busting, and allowing unchecked capitalism to depress wages while skimming the profits off the top and socializing the externalities reduces bargaining power.