Factory workers as a group had a major impact on WWII because WWII was a total war, a war in which all parts of a society had to be mobilized to contribute to the war effort.
WWII was won by the side that could produce the most war materiel. It was won by making more tanks and more airplanes and more bullets and more uniforms. The Allies won largely because they had the United States on their side. The US had a huge industrial capacity and one that could not be bombed by the enemy. This was extremely important in winning the war because, as the link below tells us,
Victory in World War II depended, more than anything else, on supplying armies with huge quantities of industrial products.
So, factory workers impacted the war by producing the materials that allowed the soldiers to fight. Whichever side did this better would, and did, win. Once again to quote the link,
The people who built these products ... were as important to the war effort as the soldiers in the armies.