Fact is, Hollywood moguls of the time had a much closer understanding of the American people as a whole. Most had actually BEEN poor in their early lives, and had worked their way up. They knew where the money was, and they were, after all, Americans. They knew that those whose husbands, brothers, fathers, friends, etc. who were going off to fight would WANT to see them portrayed as kicking the crap out of the "japs" and "krauts", and doing so in a typically American gallant fashion.
However, times now, and the entire industry, is so different that such a massive show of support would be impossible even if the studio owners wanted to do it.
And America is a much worse place,because about 98% today's studios/writers/actors/actresses/directors are faaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaar left cretins,most of whom are talentless and anti-America.