Why do the people who run the world and start wars do what they do? I have a suspicion that they don't really know what they're doing any more than anyone else knows exactly what he is doing in life and why. So you can't say a certain war is about one thing really, or for or against one country; it's just a mish-mash of all the motives and reasons that the leaders involved have, (with the followers having their own mostly misguided personal reasons of career or of religiously felt duty to serve.)
There are some loose political groupings of leaders who push certain wars, and without whom those wars wouldn't have happened. For instance, the Neoconservatives (the writers and Bush administration appointees, not every Joe in the street pro-war Republican) were indispensable to the war on Iraq happening. But many things are necessary causes to a major event. Somehow the Neoconservatives and the pro-war sentiment of media figures had to influence the Republican presidential primaries in 2000, to get a Bush in, knowing that Iraq was already a likely war, obviously since US planes were still bombing Iraq regularly under Clinton, in order to have someone in office who would be strongly personally motivated to finish what his father started. Otherwise, with another president with personal attachments to some other region of the world and a tendency to select appointees with similar concerns, the next war might have been fomented and prosecuted against some other country.
What good does continuing the war against Iraq do? How long will Iraqis see foreign soldiers fighting in their country and provoking their young men to take revenge on behalf of their families and honor? I doubt that fans of the US will ever learn to see this from their point of view, even if it lasts fifty years. The schools will still teach about the patriotism of the American Revolution, and still teach that the nationalism of other countries is a horrible thing, and that the rest of the world is better off when it has democracy brought to it by the US. There's nothing to learn from the war for the public.
Does it make oil cheaper, to be fighting over the oilfields and pipelines? Probably not. So really, the war is in the interest of, let's see: oil money (which includes the Bushes,) and super-rich schemers who want to limit the world's use of energy so that their capital is worth more relatively and controls the world more, and so-called liberals who want to limit the use of energy by something like the Kyoto Accords or whatever means necessary, so that their plans for a world socialist order will seem closer.
War conceived for an evil purpose, prosecuted by evil means, directed against the interests of those called to fight it, and lacking any possibility of conclusion except by annihilation of one side or the other: That's par for the course with human beings.