saudi arabia really isn't a real country, it's a crime family with a large fief. it would likely split into 3 or 4 smaller countries that are more similar to nation states if it were to collapse.

the strength of the saudis is on paper. the reason they don't use their army is that the aristocracy doesn't trust it. it has no loyalty to the state. a situation like we saw in iraq with isis or afghanistan with the taliban - where the superior security forces gave up without fighting - is not just plausible but likely. it would force the country to splinter quickly.

https://blogs.timesofisrael.com/could-saudi-arabia-collapse-and-would-islamists-fill-the-vacuum/