The Japanese had a legacy of democracy, going strong actually before the militants won everyone over. It was easy to return to after the ultra nationalists were so thoroughly defeated.
Also a competent beurocracy which had begun to embraced merit over croneyism and nepotism, in fact gotten farther along those lines than many allied countries.
Afghanistan is still based around tribal leaders and local allegiances. Much of their recent national identity comes from the Taliban and defeating the Russians. Maybe the only thing that can hold a country like that together is a larger than life nationalist, a tyrant. Or maybe that's defeatist, I don't know.