I have my father-in-law’s leather helmet, and it is younger than 100. They may not have been as big, but they hit. Go look at the bloody photos of players during and after games from that era. Now, most players hardly wear pads, and hitting is a penalty.
Broken noses, cauliflower ears, missing teeth and lacerated scalps are just nature's way of letting you know that your noggin is taking a beating, and that you should do something protect it. Modern protective equipment greatly lessons all of those injuries, and thus lessons nature's signals. But modern protective equipment does not keep your brain from bouncing around inside your skull when you get hit, or hit someone, hard enough.
Sammy Baugh was whip smart at 80. Many modern players are mumbling and shaking in their 50s.