Why a restored Kaiser does not settle the invasion of Poland

If the Kaiser returned to power three weeks before the invasion of Poland, would Germany still invade?

There is no single outcome because a ceremonial restoration and a violent Nazi succession crisis would produce very different governments.

The mechanism of restoration decides what follows. If Nazi leaders merely installed a monarch as a ceremonial figurehead, the regime's plans might continue with little change. A restoration caused by Hitler's removal and a struggle among Göring, rival party factions, and monarchist business interests could disrupt preparations for the invasion of Poland. Wilhelm II would also die in 1941, so the faction controlling the restoration could select a more convenient crown prince.