I don't find it surprising that most people in the world - past and present - find Christianity incredible, ridiculous or outrageous - at any rate: unbelievable. That was how it struck me, for most of my life.
In the West this is mostly because the official assumption of all adolescents and adults in public discourse - is that there is neither purpose nor meaning to human life: it is all a consequence of abstract processes, grinding-away because that is what they do.
But in most of the world, where a God is believed and assumed, Christianity is recognised to be an assertion of the limitations of God: that God is a person, and concerned with this world. For many that is a human limitation imposed on an unknowably great God - who can only be discussed indirectly, by negations and abstractions.
And, most strongly, other religions recognise that for Christians God is limited. Non Christians recognise that Christianity is an assertion that God is Not omnipotent - that there are things God cannot do. Such is implied by the Christian assertion that Jesus Christ was necessary.
If Jesus is necessary (and assuming he is not just a projection of God, an 'avatar') then there is something vital that God could not do; and that Jesus was needed to do.
This seems obvious to other religions; and it really ought to be obvious to Christians; however most Christian intellectuals deny these obvious inferences. Many Christians assert that God is omnipotent and also needs Jesus, who is a different person than God. Christians assert that God is unknowably great - omnipotent, omniscient, omnipresent - and also loves each individual person as a Father.
And this is, and always has been, a weakness of Christianity; a weakness that looks very much like dishonesty. Christians should stop attempting to 'have it both ways'; and to admit that - increasingly this fails to convince, for the simple reason that it does not make sense (at least, it does not make 'common sense').
If Jesus Christ is regarded as a fact and as a necessity; then it ought to be possible for Christians to accept the implications of that core belief - rather than to insist on fitting this into an idea of God as impersonal and abstract, all-powerful, and not-human: utterly alien - a concept that was, ultimately, derived from Non Christian religions.