He was afraid that Britain would ask for those territories as a part of their armistice so he decided to sell them quickly to the US and earn some money for the country while messing with Britain.
At the Yalta conference, significant concessions were made to the Soviet Union because the Western Allies wanted Soviet Union to join them in their war against Japan. The Yalta Conference was held in the month of February of the year 1945. This conference was held between the British Prime Minister, the Soviet President and the President of the United States.
The heat and people that go to hell make it worse(lol I can’t think of anything)