How could citizens reject a perfectly progressive constitution?

General Augusto Pinochet and the military junta in Chile in 1973. Source: AP

This month, by a plebiscite, Chileans overwhelmingly rejected a new left-leaning constitution. Reuters described it as being one of the world’s most progressive charters. The vote to approve it wasn’t organized by some elite group managing a phony election under an authoritarian government. It was a fair election, with both the left- and right-wing parties accepting the results.