Oil is for more than gas
Yes, but
most oil is used for fuel of some kind (either petrol or for power plants), and we need to stop burning it or the environment is screwed.
resource management is about having the resource to manage
Of course, but that doesn't mean wasting effort conquering areas you don't need to conquer. Particularly if those areas aren't particularly supportative.
The Harway's philosophy seems to be based somewhat in Western countries. It figures that the Middle East wouldn't be inclined to join. And, declaring war on them is a big step, particularly if the people aren't willing to just give in.