Dialectic of Enlightenment never explains the genesis of the secret utopia

Evidence

But how was the genesis of such forms to be explained? Even if explicit historical-materialist conditions were to be given under which communication with the secret utopia within the concept of reason, normally suppressed, could temporarily shape manifest history (as in the case of the bourgeois family in the liberal capitalist epoch), the question would still remain: how did the secret utopia come into existence at all, and what was it that preserved it against the irresistible process of demythologization Horkheimer and Adorno were reconstructing? — Rolf Wiggershaus, The Frankfurt School, 1390