(Not intending any rudeness, just speaking direct here.) The materialist explanation is that not everything has a 1:1 base:superstructure connection, since it'd be weird if human creativity was meaningless. It should be noted that "base determines superstructure" is a mistranslation of Marx:

You will notice that Marx does not say simply 'base determines superstructure'. The word 'determines' is actually 'bestimmt' which does not imply causation in Hegelian terminology! Marx is saying that the legal and political structure, and the content of social consciousness corresponds to the form of social productive relations. How can social relations cause you to act in ways which can be determined in the way we can predict natural scientific phenomena? If that was the case everyone would act the same as everyone else in their class, but they don't because they are individual human subjects.

Can you imagine feudal relations of production without the legal/political/religious culture of the middle ages? Can you have feudalism without lord and serf? Can you have lord and serf without peasant and nobility? Can you have peasant and nobility without the monarchy and clergy (in some form)? Can you have this system without it being reflected in the law? Can you have at the same time slavery and The Declaration of the Rights of Man? If Caesar implemented the Rights of Man would the Roman World become free market capitalism? As is the case with everything else, the content of a society's consciousness corresponds to the form of society.