Why is there no credible evidence that this 'jesus' character of the bible ever existed?

Why were the gospels written decades after the supposed date of the crucifixion? Why do people believe in an imaginary, invisible, improbable, immaterial, magical sky monkey and 'his' ZOMBIE 'son'? Do people just NEED to believe crazy $hit, or are some people just crazy and that's WHY they believe CRAZY $hit?