Its not really expected for non-Japanese to understand this but KnY speaks to the underlying nationalism of Japanese people at a time when Japan needs more nationalism. It's explicitly set in the Taisho period when Japan was its most nationalistic with a strong sense of self pride and the current government/US influence has been doing everything to hide/undermine it.
KnY is basically Sanseito in anime form and Japan (especially the younger demographic) instinctively yearns for stronger national pride.
Its also a short series so its easy for braindead normies to get in and out of.