A religion becomes "not an option" once it provides a salvation of after life by a god advocated in that religion. To put it another way, if a religion is not about after life, you may simply choose to ignore it as it won't affect you or your life. The advocate affects us because no humans can get to know what could possibly happen after death. If you believe "nothing happens" (an implicit belief of the atheists), it remains your faith to believe so. If you believe that "something happens", it remains your own faith to believe so. Both cannot be confirmed. Even it's a truth it's beyond human technology to reach. So it's your choice to choose one of them.
It's analogue to when you are tied up in a pair of rails without telling you whether a train will come by. It's up to you decide whether to believe that "no train" is coming, or it's possible that "a train is coming". A religion in this case is an advocate that "a train is coming" and "a god can save you".
So the first question to ask is, why the god doesn't show up. If you as a superior and powerful human claims to save a nest of bees, it's no point for you to remotely ask them to believe but insists not to show up in front of them. Similarly, if a powerful god claims to love you so much and so much then what's the point for him to hide behind instead of showing up in front of humans? To put it another way, the loving god chooses to hide behind must provide a good reason why he's not showing up.
The good reason the Christianity God can provide is that all humans are tied to a covenant which demands them to have faith in God in order to be saved. So if God shows up, it means humans can no longer be saved. (the next question can be why such a covenant exists, it also has a good reason but it may be off topic in this thread).
Now and for a good reason, the god will have to hide behind. Then the next question is, what efforts should he puts forward to save humans. He should first choose the most possibly efficient way to convey his message of both the warning and salvation to as many humans as possible. Other than directly showing up, the next most efficient way for a truth to convey among humans is by "believing in accounts of human witnessing". It seems to me that only the Christianity God ever knows about this efficient way, not even today's humans can realize how efficient and fundamental human witnessing can be.
This way of conveying truth has two crucial factors. One is to spread as widely as possible while the other is to invite faith to believe. It's more or less resembled to our daily news. Our media will broadcast as widely as possible to reach the many humans, and for them to believe with faith. That's the way how a truth propagates among humans.
Now the god has a good reason to hide behind, and he has chosen the most possibly efficient way to convey his salvation message, then the next question is can he keep his message consistent across history, and for humans today to receive the same salvation message as humans some 2000 years ago, and as humans in the future?
In Christianity, we can reconcile the Bible with its contents some 2000 years ago for us to tell that the Christianity God is conveying the same theological message yesterday, today and tomorrow. We have a whole library of ancient scrolls (Dead Sea Scrolls) for us to confirm the contents of the OT books. We have 2 independent sources of NT, namely the KJV and NIV streams of Bible, for us to confirm that the same NT books we read today remains theologically the same some 2000 years ago. We have whole Church which ensures that the same theology will remain with no contents added or subtracted.
Now Christianity is about a God who has a good reason to hide from humans, He employs the most efficient way to convey his message of salvation, He maintains the theological consistency of his Bible through history and the coming future for humans to receive the same message and to be saved.