That's because nobody knows that he is not a Muslim. When did he convert? Where was he baptized?
Belonging to that whacked-out Jeremiah Wright hate-group doesn't make him a Christian any more than belonging to the Westboro Baptist "Church" does.
We don't even know if he is a US citizen.
Even if he was born in the USA, what nationality was he when his family moved to Indonesia? What nationality of passport did he use to travel to Pakistan?