That's a good question, to which I don't know the answer, but I would guess that it is @ least partially due to do w/ an authoritarian monarchy that came to power by aligning itself w/ religious fundamentalism:

> The emergence of what was to become the Saudi royal family, known as the Al Saud, began in Nejd in central Arabia in 1744, when Muhammad bin Saud, founder of the dynasty, joined forces with the religious leader Muhammad ibn Abd al-Wahhab, founder of the Wahhabi movement, a strict puritanical form of Sunni Islam. This alliance formed in the 18th century provided the ideological impetus to Saudi expansion and remains the basis of Saudi Arabian dynastic rule today.

https://en.wikipedia.org/wiki/Saudi_Arabia#Before_the_founda...