Obscurantism (/ɵbˈskjʊərəntɪsm/) is the practice of deliberately preventing the facts or the full details of some matter from becoming known. There are two common historical and intellectual denotations to Obscurantism: (1) deliberately restricting knowledge—opposition to the spread of knowledge, a policy of withholding knowledge from the public; and, (2) deliberate obscurity—an abstruse style (as in literature and art) characterized by deliberate vagueness.[1][2] The name comes from French: obscurantisme, from the Latin obscurans, “darkening”.

From https://en.wikipedia.org/wiki/Obscurantism

See also Agnotology: study of disinformation propagation and Mesofacts and the lingering effects of propaganda