"Section 349 of the Immigration and Nationality Act (8 U.S.C. 1481), as amended, states that U.S. citizens are subject to loss of citizenship if they perform certain specified acts voluntarily and with the intention to relinquish U.S. citizenship. Briefly stated, these acts include:
1. obtaining naturalization in a foreign state (Sec. 349 (a) (1) INA);
2. taking an oath, affirmation or other formal declaration to a foreign state or its political subdivisions (Sec. 349 (a) (2) INA);"
The acceptance of an Indonesian passport is prima facie evidence for the relinquishment of US citizenship.
What you failed to include is those acts must be performed as an adult. A minor child cannot relinquish U.S. citizenship and they cannot have it relinquished by someone on their behalf.
Also, had Obama been adopted by Soetoro then under the Indonesian law in effect at that time he was most likely too old to have Indonesian citizenship granted to him. He would have had to apply for naturalization when he became an adult. By that time he'd been living in the U.S. again for years.