It’s definitely a combination of both but I think oil wealth is inherently destabilizing because it tends to be concentrated in areas which were not previously

It’s definitely a combination of both but I think oil wealth is inherently destabilizing because it tends to be concentrated in areas which were not previously rich and densely populated (most of the world by area) and because the way the market works allows a relatively small number of people to be wealthy without much local support compared to, say, high-end manufacturing which require lots of skilled workers and local investment. Norway is basically the only example of a petrostate where the money is invested in the betterment of the entire country.