Everything is complicated, and we live in a world of high causal density, but that does not mean we should throw up our hands in dismay and self-pity.
It is clear that the union is exploiting its monopoly on the supply of port labor, to decrease efficiency, and increase costs and union membership. For some reason, most people are less likely to attribute high costs to monopoly unions, but more than happy to do so for monopoly corporations.
Effectively, "it's complicated".