Why didn't we take Iraq's oil?

Trump said it in his terrorism speech yesterday:

I have long said that we should have kept the oil in Iraq – another area where my judgement has been proven correct. According to CNN, ISIS made as much $500 million in oil sales in 2014 alone, fueling and funding its reign of terror. If we had controlled the oil, we could have prevented the rise of ISIS in Iraq – both by cutting off a major source of funding, and through the presence of U.S. forces necessary to safeguard the oil and other vital infrastructure. I was saying this constantly and to whoever would listen: keep the oil, keep the oil, keep the oil, I said – don’t let someone else get it.

If they had listened to me then, we would have had the economic benefits of the oil, which I wanted to use to help take care of the wounded soldiers and families of those who died – and thousands of lives would have been saved. This proposal, by its very nature, would have left soldiers in place to guard our assets. In the old days, when we won a war, to the victor belonged the spoils. Instead, all we got from Iraq – and our adventures in the Middle East – was death, destruction and tremendous financial loss.

It sounds extreme — especially "to the victor belonged the spoils." The idea should be that the oil should cover the expenses of liberating and protecting the people of Iraq. Nearly everyone seems to have forgotten that the Bush administration talked about the Iraq invasion in these terms:

Ahead of and shortly after the US invasion of Iraq in 2003, a number of officials, including former Defense Secretary Donald Rumsfeld and his deputy Paul Wolfowitz suggested the war could be done on the cheap and that it would largely pay for itself. In October 2003, Rumsfeld told a press conference about President Bush's request for $21 billion for Iraq and Afghan reconstruction that "the $20 billion the president requested is not intended to cover all of Iraq's needs. The bulk of the funds for Iraq's reconstruction will come from Iraqis -- from oil revenues, recovered assets, international trade, direct foreign investment, as well as some contributions we've already received and hope to receive from the international community." In March 2003, Mr. Wolfowitz told Congress that "we're really dealing with a country that could finance its own reconstruction." In April 2003, the Pentagon said the war would cost about $2 billion a month, and in July of that year Rumsfeld increased that estimate to $4 billion.