Aside from the refugees being driven out by the Nazi's racial policies, German refugees who had become homeless during the bombings of Dresden and Berlin moved to other parts of Germany
By January 1945 the Russians had invaded Germany and millions fled to the Western cities, placing more pressure on cities already strained by bomb raids
By 1945, the Allied powers had invaded Germany. From then on, the collapse of the Third Reich was inevitable. Hitler was nowhere to be seen and all morale was lost