Fighting is rational when the alternative is being killed.
FDR made a big mistake announcing that he was going for unconditional surrender. This resulted in Germany fighting to the bitter end. Hitler dragged it on to the last few hours - he knew what was going to happen to him when the war ended.
It was not mistake. Nazi dragged because they had to due to own ideology.
But allies had to achieve clear military victory, because of WWI aftermath. Germany did not believed it lost, it believed it was betrayed and wanted do-over. No surrender thing was to prevent next round with WWIII as Germans feel like betrayed again.
The Germans had a saying at the time: "enjoy the war because the peace will be hell".
They were correct.
> Germany did not believed it lost, it believed it was betrayed
The citizens were not that stupid. They knew by 1944 that they were going to lose. All they had to do was look up, and see the ever-growing endless streams of B-17s overhead. They knew what the Red Army was going to do to them. They knew payback was coming from the Allies.
FDR made a big mistake announcing that he was going for unconditional surrender. This resulted in Germany fighting to the bitter end. Hitler dragged it on to the last few hours - he knew what was going to happen to him when the war ended.