Answer:
"They seemed to be waiting for the Reich to fail" means that the Soviets appeared to be watching and waiting for the German army to be defeated or weakened, perhaps hoping that the German war effort would collapse or that the Soviet Union would be able to take advantage of a weakened German state. In this context, "the Reich" refers to Nazi Germany, led by Adolf Hitler, which was engaged in a massive war effort against the Soviet Union and other Allied powers during World War II. The statement suggests that the Soviets were not actively engaged in fighting the Germans at that moment, but were rather biding their time and waiting for an opportunity to strike.