>>64132939
The force from a strike with a quarterstaff will kill an armored knight. Physics doesn't care if you understand it or not.
Helmets (ancient armor) is for deflection. Helmets are very good at that. That is why breastplates are curved. The war hammer, flail, quartestaff were the bain of the armored existence. Arms still break. Direct head strikes still result in death.
Swords, slashes, spear stabs, arrows however are deflected.
This isn't a movie or a video game. The quarterstaff bent and broke swords. The war hammer mounted was devastating.
If you dont understand feel free to go put on the most modern best built football Helmet made with all the best technology we have today and let Aaron Judge put a bat across your head and see what happens. Then if you recover from that try it with a thin sheet of metal and some cloth wrapping.