A somewhat strange article on Open Democracy, partly as the title indicates the military is in focus and there is very little mention of them:https://www.opendemocracy.net/arab-awakening/hesham-shafick/why-is-military-coup-in-saudi-arabia-possible?

Plus no distinction is made between the various military bodies, notably the Army and the National Guard.

What I did find interesting was the argument that:
First and formost, the kingdom has lost most of the historical roots of its legitimacy. Since the foundation of the modern kingdom, its legitimacy has been grounded on three main pillars: Sunnism, nationalism and kinship......As for the third pillar, theocratic legitimacy, it is about to fall, particularly after the kingdom’s decision to terminate the powers of the official Wahhabistagency that reinforces Islamic order – the 'Organisation for the Prevention of Vice and the Promotion of Virtue'.
I recall long ago a British diplomat talking at an event that the UK had two nightmares, a military coup in Saudi Arabia and Pakistan - each with an Islamist or radical tinge. Somehow he'd forgotten Gadafy's coup in Libya, which had consequences for the UK and others.