what about the nature or warfare during world war ii made the ability to produce war material so important?

The correct answer to this open question is the following.

The nature of the warfare during World War II made countries to develop the kind of technology applied to weapons that would favor them during the many war confrontations in different parts of Europe, the Pacific Ocean, and North Africa.

Hitler had invested so much in developing the kind of weaponry and army that could conquer and defeat its enemies. The German Army was strong, solid, well prepared and had modern and powerful weaponry that was used to capture many places, including strategic France.

In the case of the Allies, the United States invested millions of dollars in developing the right kind of technology that produced atomic weapons like the ones launched over Hiroshima and Nagasaki in August 1945, which made Japan surrender and to end the war.

Because the war was wide spread and there was a need to supply millions of soldiers and sailors with the materials and machines they needed to fight. This was a true world war with fighting going on in much of the world.

As an example: the war in Europe might have lasted a year or two longer if it had not been for the ability of American to quickly produce all of the landing craft needed for the D-Day invasion.