Why do Christians become Christians?

[Mister Agenda]

Has anyone ever "come to Jesus" without having heard about him and the stories surrounding him for long periods?

I think not. The seeping in of ideas surrounding you is not surprising. People independently describing "meeting" Jesus, while isolated from any mention of him, would be surprising.

In short, people are very susceptible to the appeal to popularity fallacy. If many people seem to believe it, it appears a reasonable belief.

Yes, of course they have. As an example, Billy Graham has spoken to millions of people in large events specifically designed to reach unbelievers. They respond to the message by the thousands--many with discussions and conversions on the spot. People who do profess or who are interested in learning more are assigned to a local church for followup.

You seem to be using the term 'unbeliever' EXTREMELY loosely.