Germany ran out of manpower. Japan didn’t belong in WW-II in the first place, but Hitler had a dozen ways to win WW-II and two or three ways to lose it and found the two or three ways. Simplest path for him to win was not to invade Russia. Russians I’ve spoken with who were alive at the time have said the place would have fallen apart on its own in another four or five years and Germany could picked up the pieces for free. Not invading Russia would also have solved the manpower problem.
Thank God Hitler was too impulsive to secure his fuel supply before invading Russia.