Mostly propaganda, to seed divide among Asian comminuties.
Holohoax used to create anti semitism and prop up Nazism as world boogeyman, meanwhile in Russia killing millions. World fascinated by Holohoax, not that people didn't die in work camps within Germany.
Similarly this and nanking massacre is used to justify bombs dropped on Hiroshima and Nagasaki, meanwhile in China.. Communist regime kills millions.