Well a lot of people do not believe because the amount of religions in existence. Christianity believers only take up less than 40% of the global population. The moon landings and the holocaust have physical proof like the bottom stage of the lunar lander still on the moon and the many concentration camps in Europe. All we have is the bible. Also with christianity taken inspiration from the pagan holidays.
Well obviously i don't know the link between the Bible and science is cause one is through hundreds of years of research and understanding and the other from a book written decades after the crucifixion of Jesus (Yes i know the original bible was not a book)