First possibility: Bush could be after the oil in Iraq for the benefit of American oil companies. Well, since France, Russia and China already have potential deals in Iraq, American oil companies may have the least to gain. Although the leader of the exiled Iraqi National Congress has promised oil contracts to US companies if US puts the exiled group in power, the benefits here would be far greater for non-American oil companies. I don't believe for a second that existing oil deals with F/R/C would be scuttled. Anyway, if helping American oil companies were Bush's aim, he could do so vastly more efficiently by giving the money that a war would cost to the American oil companies. Another way of benefitting American oil companies is by affecting the price of oil to keep it unusually high, but this is typically considered unacceptable and politically stupid because consumers (voters) suffer. Rather than see conspiracy in US actions, why don't protesters see at least as much venal conspiring in the F/R/C positions? They're the ones making oil deals with Saddam.
Second possibility: Bush could be after the oil in Iraq for the benefit of the American oil consumers. This one doesn't make a great deal of sense, because US already trades food for Iraq oil. Low prices benefit American oil consumers, but this extended saber-rattling is adding a risk premium of $5-$15 onto the price of a barrel. If Bush just wants to keep the price of oil down, he could ignore Iraq. Finally, note that keeping the price of oil down benefits Europeans at least as much, because in most European countries the price of oil is inflated by taxes. The only way Bush could help American oil consumers without helping global oil consumers would be by subsidizing imported oil.
Third possibility: Bush might wish to protect the oil in and around the Arabian peninsula (Kuwait, Saudi Arabia) from future Iraqi agression, in order to benefit American oil companies. Would this really benefit them? It depends on how many deals American oil companies have in the area. If the entire Arabian peninsula were taken offline, the price of oil would definitely go up, and this would presumably benefit American oil companies rather than disadvantage them. Again, this would benefit any oil companies working in the entire region, not just American companies.
Fourth possibility: Bush might wish to protect the oil in and around the Arabian peninsula from future Iraqi agression, in order to benefit American oil consumers. However, Europe depends more on Gulf oil than US does. So really, Bush would be helping oil consumers worldwide if his plan worked.Krugman believes this is what Bush is doing according to a recent NYT editorial.
If you believe in one of the latter two scenarios, then just perhaps, Bush is defending people as well oil from future Iraqi agression -- Kuwaitis, Israelis, Kurds, possible American and European terrorism targets. It's impossible to tell if his motivations are limited to oil. How would one prove this?