The difference between being unwillingly ignorant and being ignorantly stupid is not knowing something, and thinking that someone that does know something is pompous.

Now, I'll give you the benefit of the doubt because you're a .de Lemmy, but in American Best Buy, the people op is talking about are supposed to be salespeople who's job is literally to know basics about what they're selling. There's even people dedicated to each department for that reason. Kind of like Power, if you have that there (we have it in Finland but I know it's Swedish).

Or to put it in a term you might know, imagine going to a car dealership, and the salesperson doesn't know if the gasoline car they're saying you should buy is a V4 or V6, and can't tell you how many MPG it gets. They just know it's a car made by (brand).