If I was born in Iran I'd be a Muslim because I'd be beheaded for not being Muslim. Only one reason Islam is afraid, but that's for another topic.
I don't hear a lot of Iranians who come to America to escape Islam say that they were secretly Christians.
You know you can secretly believe the truth? That's what us atheists do when we go to church. We don't tell the priest and members we think they are stupid. We just go along. So too could Muslims in Iran. They've heard the Jesus stories. Just quietly believe. But they don't. Neither do Chinese people. They've all heard about Jesus. If it were obviously true, they'd be converting by the millions.
And if it were really true, what better reason to revolt? But I don't think they are believing the Jesus stories just like you don't believe what they say about Mohammad.
And consider all the Muslim Americans who don't convert. If it were obviously true they would, but it isn't.