It's all about oil, land and water. Ideology is about your country being the best. Everything else is irrelevant.
When I look at the foreign policy of my country (Sweden), it seems a large part of it is decided as part of internal political posturing. Tail wagging the dog, etc.
I'm not as knowledgeable about the US politics, but it seems to not be as bad -- but still a large influence.
I agree that not "everything" on the lowest level (single politicians) is simply "oil" but even looking at your example the motivation on the lower level is surely to keep the power and influence by these who already have it and to get the power and influence for these who don't have it. The next step is to ask what the power and influence does in total, what are the interests of the whole systems.