Let's say betting websites existed during WW2. If people made odds for who would win the war, what would the odds be throughout the timeline of the war? What would be the key events where the odds would change significantly?
The short answer. In 1942 there was a perception that the odds had shifted in favour of the Allies. The US had entered the war. The 6th Army was encircled at Stalingrad. Soviet resistance and counterattack were stronger than anticipated. The German advance in the Caucasus had halted and troops would be withdrawn in 1943.
Speer described a shift in attitude at Fuhrer HQ during this year, from optimistic to sullen.
In 1944 the Allies achieved air supremacy and landed in Normandy, which again were perceived to shifted odds significantly.
Certainly many more factors, such as every lost skirmish in the East, but these are a handful of "big" events.
Interestingly in some infantry memoirs I've read, attitude among ground forces was not completely pessimistic. Many believed they would be able to hold the Red Army at the German border, and would receive Allied support in fighting the Russians. Same thing with senior politicians, who were jostling for power and planning successor governments until the very end, under the assumption the Americans would negotiate if they (the Germans) continued to resist the Russians.