You guess wrong. There is a lot of evidence that disputes where Obama was born, including his wife's own words, but not so much to dispute that he was an Indonesian citizen at this time in his life. I assume you're still conceding the point.
The only evidence you have to support the claim that he was an Indonesian citizen also claims he was born in Honolulu. So if Soetoro was lying about where he was born why couldn't he be lying about his citizenship?