Why did the Nazis get rid of the einzatsgruppen?

They were established in 1942 in the Soviet Union and were divided into 4 units if approximately 600 men: A B C D groups. Once the Germans were finally ousted from the Soviet Union in late 1944, these groups were disbanded because of the chaos and constant retreats. The vast majority of Polish Jews were murdered by 1944-45 for the retreating einsatzgruppen to roundup and murder. Genereal Ohlendorf, who commanded the einsatzgruppen D, was captured and tried as a war criminal at Nuremberg after the war. What makes his case so interesting, is that he was very open and honest about his crimes on the eastern front and accepted his guilt. He was executed by hanging soon after the verdict.