There's a God and we do not need science to prove His existence to us
This is true. The idea is to show atheists that God exists in language they understand, before they die in their sins. Obviously, many of them will simply pull back into their shell rather than seek God and a joyful eternal life in Heaven. But a few of them will turn. And many border-line Christians will see how God truly DOES exist, and will be strengthened in their Christianity.
How did you choose to believe in christianity in the first place?
I heard God's words from the Bible. The Holy Spirit worked faith in my heart. I happened to not be one of the obstinate ones who was so stubborn that I had the ability to resist the Holy Spirit. Rather, at that time I was weak in spiritual strength.
Perhaps my obstinacy has grown. Perhaps if I didn't see the logic of God now that I have experience with Him, I might resist Him along with the atheists.