There are physical karmas that carry through death. Jesus Christ may no longer be with us but his effects continue on in the world. Those waves will be passed on from one person to another to another.
You can focus on Jesus or Buddha or Krishna, Ramakrishna, Lao Tsu, Yukteswar, Yogananda, Vivekananda, any of the great spiritual teachers who have lived, or on a living teacher, and draw light from them.
Christianity is a marketable product. It has very little to do with Jesus Christ. I'm sure it has nothing to do with Jesus Christ at all - what the experience was like to be around the guy.
If a spiritual being is naive to the lower aspects of the world, they usually are killed or die young. Did Jesus really know which of the twelve would betray him? I doubt it.
Jesus Christ was a simple man walked around, did a few miracles, said a few things and died. It was enough for him to say what he felt and glow with the light of eternity.
I would say that Jesus Christ and his followers were a cult, Buddha and his followers were a cult and Mohammed and his followers were a cult. Every religion starts out as a cult and if it becomes 'box office', it is accepted.
