Put your mind back.
>Smokeless powder had been in wide-spread use for less than 60 years when ww2 ended.
>Smokeless powder opened up entirely now avenues for firearms that had been limited by Black powder
>institutional and industrial internia slows things down (you need a long barrel and big bullet to get the most out of BP, you need a long barrel and Big bullet to make the most out of the new smokeless.
>The advent of smokeless had generals thinking that riflemen would make artillery unnecessary because now they could shoot over kilometers
>thinking was still based around mass formations and controlled fire, the individual solider wasn't expected to think
Look at any comparative technologies and you will see it went though many changes before you get the refined products we have today
>what we're they thinking when they designed the first cars? Why didn't they use the design we use now