Why Did the Nazis Treatment of the Jews Change from 1939-45?

On January 20, 1942 fifteen high ranking Nazi party and German government leaders gathered for an important meeting. They met in a wealthy section of Berlin to discuss a topic only known as 'The Final Solution'. The Nazis used this vague term to hide their policy of mass murder from the rest of the world; they were to remove the Jews from German society.
In 1939 Germany invaded Poland and 2 million Polish Jews came under Nazi Control.
…