One answer to this question is because Christianity is falsifiable.
Consider the flurry of sensory verbs in the first two verses of 1 John 1:
That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands, concerning the word of life — the life was made manifest, and we have seen it, and testify to it and proclaim to you the eternal life, which was with the Father and was made manifest to us. (emphasis mine)
This kind of language is a reminder of the historical nature of our faith. At the heart of what we believe as Christians are things that happened in real time in history. The incarnation, the death, and the resurrection of Christ happened.
Here are two images from a helpful article, “Christianity, The World’s Most Falsifiable Religion,” illustrating the contrast between how Christianity started and how other religions started:
Read the whole article here.