> and Herbert was a child of the 1960s psychedelic culture

Was he really a child of this culture? He was in his 40s by the time Dune came out in 1965, with large parts of it written in the early 60s, when psychadelics seemed more of a fringe thing used in beatnik circles, academic labs and prisons.

OTOH, the concept of invaders seizing territory for spice or other unique natural materials (Dutch and Portuguese in the Moluccas, Japan annexing Taiwan) drugs shifting empires (Opium) and special substances and techniques needed for long-distance navigation (citrus, astrolabe) had been around for centuries.