Forced labor continued because It was mainly for black people. Many people at the time and still are very racist. Forced labor persisted after the Civil War because it was a crime in the south for any farm worker to search for employment from a new employer without permission from the old employer.
Because Imperial Japan (an Axis power) had just bombed Pearl Harbor, which brought the U.S. onto the Allies Side (which included the UK) and Roosevelt and Churchill were planning on how to defeat the Axis.
