I am not a Christian but I do know that many of christian friends are happy with their religion and do not question it. Christianity, as you should probably know, is a faith or belief.
Belief- "confidence in the truth or existence of something not immediately susceptible to rigorous proof"
Honestly it does not really matter if it makes sense or not the Christians just choose to believe it. The religion probably makes them happy or has run in the family for generations. Who are we to force someone to try to change their beliefs. Obviously you have your own beliefs whether they are true or not. The Big Bang is still a theory along with evolution (although these are basically confirmed). Therefore, you choose to believe these are true.
In conclusion, as one South Park episode showed me all -isms are bad including atheism because everyone will still have different beliefs which will lead to conflict.