Hi Tim
I think by the mid 1930's the battleship was still considered the queen or King of the seas, all the major nations with the industry and of course cash were busy designing and building modern battleships. Of course with the collapse of the naval treaties the designers were on the loose lol. Of course there were voices about the major threat of aircraft, but they were ignored.
I was watching a YouTube video a few months back, it was a lecturer by an author of a book on why Hitler lost the war, cannot remember his name. It was very good. I was shocked to hear that in 1945 the Germans still had over 400 U boats compared to only about 45 in 1939! The author simply said, what if Hitler had 450 in 1939? In matter of months he could have brought us to our knees. So I totally agree he should not have built Bismarck and Tirpitz, but so glad he did not!!