In your opinion what causes christians to believe in Jesus

[John 6IX Breezy]

I asked them about their theological beliefs and they said they had never thought about it. It was the least important part of Christianity in their eyes.

Herbert Simon, an early cognitive scientist, popularized the term Satisficing in the study of judgment and decision making. People do not attempt to exhaust every subject and choice presented to them before making a judgment. And for obvious reasons, we simply don't have the bandwidth nor the time to maximize every decision we have to make. Instead, we aim for good enough and extrapolate the rest. So, in the case of this couple their good enough threshold was met, and it was enough to judge God's existence as real or possible, and then to focus on living a Christian life. We never get off the ground if we require absolute certainty, on any topic.