Why would he need to convert to Islam after he came back to Hawaii? He was enrolled as a Muslim in a Muslim school in Jakarta before that.
Maybe he “converted” after his supposed conversion to Christianity in Chicago, engineered by supposed-ex-Muslim Jeremiah Wright, who says he made it easy for Obama to be baptized Christian without renouncing Islam...
Hard to tell with Islam because taqiyya makes it a virtue to lie if it’s intended to further Islam.