The tl;dr for you is that the Saudi people made more people faster than their cash could make more cash. And as an extraction-based economy they made more jobs

The tl;dr for you is that the Saudi people made more people faster than their cash could make more cash. And as an extraction-based economy they made more jobs even more slowly than that. So now they've got a glut of young people, not enough cash to keep them complacent, and not enough jobs to keep them occupied. What do you think will happen next?