Three competing explanations for authoritarianism in oil producing states

Many major oil producing countries are non-democratic. Here are three plausible explanations from political economy:

1. The economy and incomes in oil producing states are created mainly by sales of a natural commodity, so that the conditions are not conducive of growth through capital accumulation. Thus the class structures which either lead to or support democracy are not present.

2. External powers support corrupt and repressive leaders because they find it more profitable to buy oil from them than from institutions and companies in free democracies. Oil is such an important commodity that most external powers act immorally when dealing with it.

3. The relation between oil and authoritarianism is an accident, with coincidence of geographical clusters of oil and states which are non-democratic for other reasons.

I've seen explanation one a couple of times in theoretical economic literature, and I am fairly sympathetic to it. Recently, events in Africa suggest that explanation two may have merits as well. I do not have strong opinions about explanation three.