You also have to consider that hats were still a regular part of a man's wardrobe during that time period so I'm pretty sure that he would replace his hats on a regular basis as some some got too beat up and nasty looking to be acceptable for wearing in public.
True. Although, you'd be surprised the kind of punishment a well-made, good-quality felt hat like that can take. I've got a 3x beaver black cowboy hat that I wore for about 18 years on horse-packing trips, deep into the mountains in Montana, and it got plenty of wear and tear. The worst thing that happened to it was that it developed a patina of dust that never went away, and the lining started to pull away from the sweat band. Now, that said, I wouldn't wear the thing to a dress event (even one in Texas, where a dress cowboy hat might be appropriate), but I didn't need to replace the thing, as long as it held its shape.
My Akubra Federation gets worn plenty during the colder weather months, and in the rain, and has traveled with me overseas and back in an airplane overhead compartment. These things can take
plenty of weathering.
Keep in mind he was a professor so he'd be buying suits from time to time, either from a tailor or a department store. Being that it was the 30's his clothier would also have had a fine selection of hats.
Tailor, almost certainly. True bespoke tailors were a
lot more common back then than they are now, and machine-made, mass-produced suits were the exception, rather than the rule. In my opinion, a man only really needs three hats total: black, brown, and grey. Although you can expand that to include more shades of grey or brown.