alt Hacker NewsMy understanding is that unique historical, cultural, and even geographical factors have led to this outcome for Oman. I would encourage you to read up on the history of the country to understand the nuance here and not paint with such a broad brush.
Everyone has a unique "..." and a nuance here and a nuance there.
UAE has a unique yada yada and also ended up with a surprisingly remarkably free economic index despite being a theocratic monarchy.
As did the monarchy Lichtenstein, British controlled Hong Kong, and the one-party state of Singapore (technically democratic, in practice it functions like a recallable monarchy).
Also of note the three richest countries by GDP PPP per capita are Monaco (hybrid monarchy with monarchist veto powers), Lichtenstein (hybrid monarchy with monarchist veto powers), Singapore (single party state).