Profession can absolutely affect volume. Even without any hearing damage, any job that regularly requires that you project can become a habit.
I’m a chemistry professor at a community college, fairly well educated, and I flatter myself to say reasonably intelligent, but I still slip into what my wife calls my “teaching voice” in some social settings or even occasionally at home.
Well, it was completed in 1941 while the US was still strongly isolationist. We didn’t enter WW2 until after the attack on Pearl Harbor, which was December 7th.
So yeah, there was a world war going on, but the statue was planned and completed while it was largely “business as usual” in the US.