Christianity works for me because it is the only way to connect with the Triune God who made us all, and wants to be there for us all. Say what you want about the Bible, it is the only collection of ink and paper that has the endorsement and enforcement of the God's Holy Spirit in its behalf. When you read a selection of Scripture, not only do your eyes behold words, but your spirit beholds God in Spirit, in a way that can't happen when reading any other text, except as it repeats His thoughts. This is what makes it work for me, because no other action than seeking Him satisfies me to the deepest places inside. Its a satisfaction that cannot be gained from any relationship to any human being. There are places in the human soul that only its maker can touch and satisfy.
People are Christian because within each of us is a sense of right and wrong. The biblical scriptures hold to truth. To believe in something never seen is so complex yet so simple. Once you've made the decision to believe an understanding envelopes you. And, peace abounds.