So most of that is either Victorian period guys making shit up about mideval Europe which is where a lot of modern pop culture interpretation is still largely based in or early modern period rich guys and maybe some mideval rich guys. Germ theory wasn’t a thing of course but there was some long observed cause and effect in regards to being dirty as hell and disease. Cleanliness was also next to godliness so mideval guys did feel a spiritual need to bathe as well to an extent. Rich people not bathing was sort of a flex in how rich they are. The idea was they aren’t out there sweating and toiling so bathing was less necessary for them. Peasants would regularly ‘bathe’ by just getting naked and jumping in the river. Washing clothes was a whole ordeal as was most domestic stuff which is partially why peasants seemingly had so many days off, those were days off from getting your lord the grain so you can do laundry, re-thatch the roof, animal husbandry shit, and also to tend your own damn grain that youre gonna eat.

Victorian guys who loved to slander and romanticize the middle ages simultaneously also lived in disgusting filthy conditions due to the recent forced urbanity which were way grosser than any mideval farm or even city but they were kinds hyped on themselves so they had to imagine the past as being even grosser