Why are British and American troops stationed in Iraq?

It is divided into two parts: on the face, it is to help the Iraqi governor maintain stability, realize reconstruction and establish a good image in his own country; The purpose of Lizi is to intimidate the Iraqi government, in order to gain the pro-American forces to come to power and gain the greatest war benefits, especially the benefits of oil and geopolitics. At the same time, it also threatens disobedient countries such as Iran. In a word, it is to earn enough face, but also real and potential economic and political benefits.