Why did the dutch kept West Papua when the gave up on Indonesia anyway? I never heard the story behind that one.
West Papua was inhabited by Melanesian New Guineans, who differed from the rest of Indonesia in culture, language and racially. Giving the territory to Indonesia would not be an exercise in self-determination, but simply exchanging one imperialist master for another. At least, that was the reasoning given by Australia at the time.
In reality, it was simply a case of the pro-independence Indonesians not actually having a force in the territory, whereas the Dutch did. The Dutch, who were already being forced to give up the jewel of their empire, didn't want to lose everything and endeavoured to hold onto the poorest, least integrated part of NEI on the grounds that it had never really been part of the NEI administration anyway.
The Australians thought that an expansionist Indonesia might have designs on Papua New Guinea or Malaysia. By denying them West Papua, it ensured that their expansionist desires were directed against somebody else, rather than us or our British masters/ allies. Simple divide and rule, there. Also, we might have the possibility of appearing as heroes later by supporting Indonesian claims to the territory - which is exactly what happened in the 1960s - in exchange for some sort of
quid pro quo regarding Malaysia (which happened) or East Timor (which didn't).
There's also the simle fact that the Indonesians themselves hadn't decided how much territory they wanted for their new state. Sukarno, who wanted the entirety of the NEI (and more) was actually in the minority in the immediate post-independence period. Many pro-independence activists wanted a smaller Java-dominated state. Some only wanted Javanese independence, while some wanted a loose confederation of all the former NEI. Only a few hard-liners even cared about West Papua. So there wasn't any concerted effort to get rid of the Dutch there until Sukarno embarked on his foreign adventures over a decade later.